merchant

taler_merchantdb_plugin.h (190490B)

---

 /*
   This file is part of TALER
   Copyright (C) 2014-2026 Taler Systems SA
 
   TALER is free software; you can redistribute it and/or modify it under the
   terms of the GNU Lesser General Public License as published by the Free Software
   Foundation; either version 3, or (at your option) any later version.
 
   TALER is distributed in the hope that it will be useful, but WITHOUT ANY
   WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
   A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
 
   You should have received a copy of the GNU General Public License along with
   TALER; see the file COPYING.GPL.  If not, see <http://www.gnu.org/licenses/>
 */
 /**
  * @file taler_merchantdb_plugin.h
  * @brief database access for the merchant
  * @author Florian Dold
  * @author Christian Grothoff
  * @author Priscilla Huang
  */
 #ifndef TALER_MERCHANTDB_PLUGIN_H
 #define TALER_MERCHANTDB_PLUGIN_H
 
 #include <gnunet/gnunet_common.h>
 #include <gnunet/gnunet_time_lib.h>
 #include <gnunet/gnunet_util_lib.h>
 #include <gnunet/gnunet_db_lib.h>
 #include <taler/taler_merchant_util.h>
 #include <taler/taler_exchange_service.h>
 #include <jansson.h>
 #include <donau/donau_service.h>
 #include <donau/donau_util.h>
 
 
 /**
  * Handle to interact with the database.
  */
 struct TALER_MERCHANTDB_Plugin;
 
 
 GNUNET_NETWORK_STRUCT_BEGIN
 
 
 /**
  * Format of the data hashed to generate the notification
  * string whenever the KYC status for an account has
  * changed.
  */
 struct TALER_MERCHANTDB_MerchantKycStatusChangeEventP
 {
   /**
    * Type is TALER_DBEVENT_MERCHANT_EXCHANGE_KYC_STATUS_CHANGED.
    */
   struct GNUNET_DB_EventHeaderP header;
 
   /**
    * Salted hash of the affected account.
    */
   struct TALER_MerchantWireHashP h_wire;
 };
 
 /**
  * Event triggered when an order is paid.
  */
 struct TMH_OrderPayEventP
 {
   /**
    * Type is #TALER_DBEVENT_MERCHANT_ORDER_PAID
    */
   struct GNUNET_DB_EventHeaderP header;
 
   /**
    * Always zero (for alignment).
    */
   uint32_t reserved GNUNET_PACKED;
 
   /**
    * Merchant's public key
    */
   struct TALER_MerchantPublicKeyP merchant_pub;
 
   /**
    * Hash of the order ID.
    */
   struct GNUNET_HashCode h_order_id;
 };
 
 
 GNUNET_NETWORK_STRUCT_END
 
 /**
  * Current exposed deposit limits by an exchange
  * for a merchant (until other rules may apply).
  */
 struct TALER_MERCHANTDB_DepositLimits
 {
   /**
    * Maximum amount to be deposited within @a timeframe.
    */
   struct TALER_Amount threshold;
 
   /**
    * Timeframe over which the limit applies.
    */
   struct GNUNET_TIME_Relative timeframe;
 
   /**
    * True if this is a soft limit that could be
    * raised (by AML staff or by passing KYC checks).
    */
   bool soft_limit;
 };
 
 /**
  * Details about a wire account of the merchant.
  */
 struct TALER_MERCHANTDB_AccountDetails
 {
   /**
    * Hash of the wire details (@e payto_uri and @e salt).
    */
   struct TALER_MerchantWireHashP h_wire;
 
   /**
    * Salt value used for hashing @e payto_uri.
    */
   struct TALER_WireSaltP salt;
 
   /**
    * Instance ID. Do not free (may be aliased with
    * the instance ID given in the query!).
    * FIXME: set in all functions involving this struct!
    */
   const char *instance_id;
 
   /**
    * Actual account address as a payto://-URI.
    */
   struct TALER_FullPayto payto_uri;
 
   /**
    * Where can the taler-merchant-wirewatch helper
    * download information about incoming transfers?
    * NULL if not available.
    */
   char *credit_facade_url;
 
   /**
    * JSON with credentials to use to access the
    * @e credit_facade_url.
    */
   json_t *credit_facade_credentials;
 
   /**
    * Additional meta data to include in wire transfers to this
    * account. Can be NULL if not used.
    */
   char *extra_wire_subject_metadata;
 
   /**
    * Is the account set for active use in new contracts?
    */
   bool active;
 
 };
 
 
 /**
  * Binary login token. Just a vanilla token made out
  * of random bits.
  */
 struct TALER_MERCHANTDB_LoginTokenP
 {
   /**
    * 32 bytes of entropy.
    */
   uint64_t data[32 / 8];
 };
 
 /**
  * Authentication settings for an instance.
  */
 struct TALER_MERCHANTDB_InstanceAuthSettings
 {
   /**
    * Hash used for authentication.  All zero if authentication is off.
    */
   struct TALER_MerchantAuthenticationHashP auth_hash;
 
   /**
    * Salt used to hash the "Authentication" header, the result must then
    * match the @e auth_hash.
    */
   struct TALER_MerchantAuthenticationSaltP auth_salt;
 };
 
 /**
  * General settings for an instance.
  */
 struct TALER_MERCHANTDB_InstanceSettings
 {
   /**
    * prefix for the instance under "/instances/"
    */
   char *id;
 
   /**
    * legal name of the instance
    */
   char *name;
 
   /**
    * merchant's site url
    */
   char *website;
 
   /**
    * email contact for password reset / possibly admin / customers
    */
   char *email;
 
   /**
    * phone contact for password reset / possibly admin / customers
    */
   char *phone;
 
   /**
    * merchant's logo data uri
    */
   char *logo;
 
   /**
    * Address of the business
    */
   json_t *address;
 
   /**
    * jurisdiction of the business
    */
   json_t *jurisdiction;
 
   /**
    * Use STEFAN curves to determine acceptable
    * fees by default (otherwise: accept no fees by default).
    */
   bool use_stefan;
 
   /**
    * True of @e phone was validated.
    */
   bool phone_validated;
 
   /**
    * True of @e email was validated.
    */
   bool email_validated;
 
   /**
    * If the frontend does NOT specify an execution date, how long should
    * we tell the exchange to wait to aggregate transactions before
    * executing the wire transfer?  This delay is added to the current
    * time when we generate the advisory execution time for the exchange.
    */
   struct GNUNET_TIME_Relative default_wire_transfer_delay;
 
   /**
    * If the frontend does NOT specify a payment deadline, how long should
    * offers we make be valid by default?
    */
   struct GNUNET_TIME_Relative default_pay_delay;
 
   /**
    * If the frontend does NOT specify a refund deadline, how long should
    * refunds be possible?
    */
   struct GNUNET_TIME_Relative default_refund_delay;
 
   /**
    * How much should we round up the wire transfer deadline computed by
    * adding the @e default_wire_transfer_delay to the refund deadline.
    */
   enum GNUNET_TIME_RounderInterval default_wire_transfer_rounding_interval;
 
 };
 
 
 /**
  * Typically called by `lookup_instances`.
  *
  * @param cls closure
  * @param merchant_pub public key of the instance
  * @param merchant_priv private key of the instance, NULL if not available
  * @param is general instance settings
  * @param ias instance authentication settings
  */
 typedef void
 (*TALER_MERCHANTDB_InstanceCallback)(
   void *cls,
   const struct TALER_MerchantPublicKeyP *merchant_pub,
   const struct TALER_MerchantPrivateKeyP *merchant_priv,
   const struct TALER_MERCHANTDB_InstanceSettings *is,
   const struct TALER_MERCHANTDB_InstanceAuthSettings *ias);
 
 
 /**
  * Callback invoked with information about a bank account.
  *
  * @param cls closure
  * @param merchant_priv private key of the merchant instance
  * @param ad details about the account
  */
 typedef void
 (*TALER_MERCHANTDB_AccountCallback)(
   void *cls,
   const struct TALER_MerchantPrivateKeyP *merchant_priv,
   const struct TALER_MERCHANTDB_AccountDetails *ad);
 
 
 /**
  * Determines the maximum @a amount for a particular
  * type of operation for a given @a exchange_url.
  *
  * @param cls closure
  * @param exchange_url base URL of the exchange to get
  *   the limit for
  * @param[in,out] amount lowered to the maximum amount
  *   allowed at the exchange
  */
 typedef void
 (*TALER_MERCHANTDB_OperationLimitCallback)(
   void *cls,
   const char *exchange_url,
   struct TALER_Amount *amount);
 
 
 /**
  * Typically called by `lookup_products`.
  *
  * @param cls a `json_t *` JSON array to build
  * @param product_serial row ID of the product
  * @param product_id ID of the product
  */
 typedef void
 (*TALER_MERCHANTDB_ProductsCallback)(
   void *cls,
   uint64_t product_serial,
   const char *product_id);
 
 
 /**
  * Details about a product.
  *
  * FIXME: reuse TALER_MERCHANT_Product as a member in this structure!
  */
 struct TALER_MERCHANTDB_ProductDetails
 {
   /**
    * Name of the product.
    */
   char *product_name;
 
   /**
    * Description of the product.
    */
   char *description;
 
   /**
    * Internationalized description.
    */
   json_t *description_i18n;
 
   /**
    * Unit in which the product is sold.
    */
   char *unit;
 
   /**
    * Optional list of per-unit prices. When NULL or empty, @e price
    * must be used as the canonical single price.
    */
   struct TALER_Amount *price_array;
 
   /**
    * Number of entries in @e price_array.
    */
   size_t price_array_length;
 
   /**
    * Base64-encoded product image, or an empty string.
    */
   char *image;
 
   /**
    * Hash of the product image data, or NULL.
    */
   char *image_hash;
 
   /**
    * List of taxes the merchant pays for this product. Never NULL,
    * but can be an empty array.
    */
   json_t *taxes;
 
   /**
    * Number of units of the product in stock in sum in total, including all
    * existing sales and lost product, in product-specific units. UINT64_MAX
    * indicates "infinite".
    */
   uint64_t total_stock;
 
   /**
    * Fractional part of stock in units of 1/1000000 of the base value.
    */
   uint32_t total_stock_frac;
 
   /**
    * Honor fractional stock if TRUE, else only integer stock.
    */
   bool allow_fractional_quantity;
 
   /**
    * Precision level (number of decimal places) to apply when
    * fractional quantities are enabled.
    */
   uint32_t fractional_precision_level;
 
   /**
    * Number of units of the product in sold, in product-specific units.
    */
   uint64_t total_sold;
 
   /**
    * Fractional part of units sold in units of 1/1000000 of the base value.
    */
   uint32_t total_sold_frac;
 
   /**
    * Number of units of stock lost.
    */
   uint64_t total_lost;
 
   /**
    * Fractional part of lost units in units of 1/1000000 of the base value.
    */
   uint32_t total_lost_frac;
 
   /**
    * Identifies where the product is in stock, possibly an empty map.
    */
   json_t *address;
 
   /**
    * Identifies when the product will be restocked. 0 for unknown,
    * #GNUNET_TIME_UNIT_FOREVER_ABS for never.
    */
   struct GNUNET_TIME_Timestamp next_restock;
 
   /**
    * Minimum required age for consumers buying this product.
    * Default is 0. Only enforced of an exchange supports age
    * restrictions.
    */
   uint32_t minimum_age;
 
   /**
    * Group in which the product is in. 0 for default group.
    */
   uint64_t product_group_id;
 
   /**
    * Money pot into which sales of this product should go into by default.
    */
   uint64_t money_pot_id;
 
   /**
    * True if the price for this product is given in net,
    * False if its the gross price.
    */
   bool price_is_net;
 
 };
 
 /**
  * Minimal product details for inventory templates.
  */
 struct TALER_MERCHANTDB_InventoryProductDetails
 {
   /**
    * Name of the product.
    */
   char *product_name;
 
   /**
    * Description of the product.
    */
   char *description;
 
   /**
    * Internationalized description.
    */
   json_t *description_i18n;
 
   /**
    * Unit in which the product is sold.
    */
   char *unit;
 
   /**
    * List of per-unit prices.
    */
   struct TALER_Amount *price_array;
 
   /**
    * Number of entries in @e price_array.
    */
   size_t price_array_length;
 
   /**
    * Hash of the product image data, or NULL.
    */
   char *image_hash;
 
   /**
    * Honor fractional stock if TRUE, else only integer stock.
    */
   bool allow_fractional_quantity;
 
   /**
    * Precision level (number of decimal places) to apply when
    * fractional quantities are enabled.
    */
   uint32_t fractional_precision_level;
 
   /**
    * Remaining units after sold/lost/locked deductions.
    */
   uint64_t remaining_stock;
 
   /**
    * Fractional part of remaining units in units of 1/1000000 of the base value.
    */
   uint32_t remaining_stock_frac;
 
   /**
    * List of taxes the merchant pays for this product. Never NULL,
    * but can be an empty array.
    */
   json_t *taxes;
 };
 
 
 /**
  * Details about an inventory measurement unit.
  */
 struct TALER_MERCHANTDB_UnitDetails
 {
 
   /**
    * Database serial.
    */
   uint64_t unit_serial;
 
   /**
    * Backend identifier used in product payloads.
    */
   char *unit;
 
   /**
    * Default long label (fallback string).
    */
   char *unit_name_long;
 
   /**
    * Default short label (fallback string).
    */
   char *unit_name_short;
 
   /**
    * Internationalised long labels.
    */
   json_t *unit_name_long_i18n;
 
   /**
    * Internationalised short labels.
    */
   json_t *unit_name_short_i18n;
 
   /**
    * Whether fractional quantities are enabled by default.
    */
   bool unit_allow_fraction;
 
   /**
    * Maximum number of fractional digits honoured by default.
    */
   uint32_t unit_precision_level;
 
   /**
    * Hidden from selectors when false.
    */
   bool unit_active;
 
   /**
    * Built-in units cannot be deleted.
    */
   bool unit_builtin;
 };
 
 
 /**
  * Typically called by `lookup_all_products`.
  *
  * @param cls a `json_t *` JSON array to build
  * @param product_serial row ID of the product
  * @param product_id ID of the product
  * @param pd full product details
  * @param num_categories length of @a categories array
  * @param categories array of categories the
  *   product is in
  */
 typedef void
 (*TALER_MERCHANTDB_ProductCallback)(
   void *cls,
   uint64_t product_serial,
   const char *product_id,
   const struct TALER_MERCHANTDB_ProductDetails *pd,
   size_t num_categories,
   const uint64_t *categories);
 
 /**
  * Typically called by `lookup_inventory_products`.
  *
  * @param cls a `json_t *` JSON array to build
  * @param product_id ID of the product
  * @param pd inventory product details
  * @param num_categories length of @a categories array
  * @param categories array of categories the
  *   product is in
  */
 typedef void
 (*TALER_MERCHANTDB_InventoryProductCallback)(
   void *cls,
   const char *product_id,
   const struct TALER_MERCHANTDB_InventoryProductDetails *pd,
   size_t num_categories,
   const uint64_t *categories);
 
 
 /**
  * Callback function typically used by `select_donau_instances` to handle
  * the details of each Donau instance retrieved from the database.
  *
  * @param cls Closure to pass additional context or data to the callback function.
  * @param donau_url The URL of the Donau instance.
  */
 typedef void
 (*TALER_MERCHANTDB_DonauInstanceFilteredCallback)(
   void *cls,
   const char *donau_url
   );
 
 /**
  * Callback function typically used by `select_donau_instances` to handle
  * the details of each Donau instance retrieved from the database.
  *
  * @param cls Closure to pass additional context or data to the callback function.
  * @param donau_instance_serial Serial number of the Donau instance in the merchant database.
  * @param donau_url The URL of the Donau instance.
  * @param charity_name The name of the charity associated with the Donau instance.
  * @param charity_pub_key Pointer to the charity's public key used for cryptographic operations.
  * @param charity_id The unique identifier for the charity within the Donau instance.
  * @param charity_max_per_year Maximum allowed donations to the charity for the current year.
  * @param charity_receipts_to_date Total donations received by the charity so far in the current year.
  * @param current_year The year for which the donation data is being tracked.
  * @param donau_keys_json JSON object containing additional key-related information for the Donau instance, NULL if not (yet) available.
  */
 typedef void
 (*TALER_MERCHANTDB_DonauInstanceCallback)(
   void *cls,
   uint64_t donau_instance_serial,
   const char *donau_url,
   const char *charity_name,
   const struct DONAU_CharityPublicKeyP *charity_pub_key,
   uint64_t charity_id,
   const struct TALER_Amount *charity_max_per_year,
   const struct TALER_Amount *charity_receipts_to_date,
   int64_t current_year,
   const json_t *donau_keys_json
   );
 
 
 /**
  * Structure to hold Donau instance details from the database.
  */
 struct TALER_MERCHANTDB_DonauInstance
 {
   /**
    * Donau instance serial
    */
   uint64_t donau_instance_serial;
 
   /**
    * The URL for the Donau instance.
    */
   char *donau_url;
 
   /**
    * The name of the charity associated with the Donau instance.
    */
   char *charity_name;
 
   /**
    * Pointer to the public key of the charity, used for cryptographic operations.
    * This is represented as an EDDSA public key structure.
    */
   struct DONAU_CharityPublicKeyP *charity_pub_key;
 
   /**
    * A unique identifier for the charity in the Donau instance.
    */
   uint64_t charity_id;
 
   /**
    * The maximum allowable amount for donations to this charity in the current year.
    * This is tracked for regulatory or internal business constraints.
    */
   struct TALER_Amount charity_max_per_year;
 
   /**
    * The total amount of donations received by the charity in the current year.
    * This field helps track progress toward the yearly donation limit.
    */
   struct TALER_Amount charity_receipts_to_date;
 
   /**
    * The current year being tracked for donations.
    * This is used to differentiate donation data between years.
    */
   int64_t current_year;
 
   /**
    * A JSON object containing key information specific to the Donau instance,
    * such as cryptographic keys or other relevant details.
    */
   json_t *donau_keys_json;
 };
 
 /**
  * Typically called by `lookup_login_tokens`.
  *
  * @param cls a `json_t *` JSON array to build
  * @param creation_time creation time of the token
  * @param expiration_time expiration time of the token
  * @param scope validity scope of the token
  * @param description description of the token
  * @param serial serial number of the token
  */
 typedef void
 (*TALER_MERCHANTDB_LoginTokensCallback)(
   void *cls,
   struct GNUNET_TIME_Timestamp creation_time,
   struct GNUNET_TIME_Timestamp expiration_time,
   uint32_t scope,
   const char *description,
   uint64_t serial);
 
 
 /**
  * Typically called by `lookup_templates`.
  *
  * @param cls closure
  * @param template_id ID of the template
  * @param template_description description of the template
  */
 typedef void
 (*TALER_MERCHANTDB_TemplatesCallback)(
   void *cls,
   const char *template_id,
   const char *template_description);
 
 
 /**
  * Typically called by `lookup_otp_devices`.
  *
  * @param cls closure
  * @param otp_id ID of the OTP device
  * @param otp_description description of the OTP device
  */
 typedef void
 (*TALER_MERCHANTDB_OtpDeviceCallback)(
   void *cls,
   const char *otp_id,
   const char *otp_description);
 
 
 /**
  * Details about a template.
  */
 struct TALER_MERCHANTDB_TemplateDetails
 {
   /**
    * Description of the template.
    */
   char *template_description;
 
   /**
    * In this template contract, we can have additional information.
    */
   json_t *template_contract;
 
   /**
    * ID of the OTP device linked to the template, or NULL.
    */
   char *otp_id;
 
   /**
    * Editable default values for fields not specified
    * in the @e template_contract. NULL if the user
    * cannot edit anything.
    */
   json_t *editable_defaults;
 
 };
 
 
 /**
  * Details about an OTP device.
  */
 struct TALER_MERCHANTDB_OtpDeviceDetails
 {
 
   /**
    * Description of the device.
    */
   char *otp_description;
 
   /**
    * Current usage counter value.
    */
   uint64_t otp_ctr;
 
   /**
    * Base64-encoded key.
    */
   char *otp_key;
 
   /**
    * Algorithm used to compute purchase confirmations.
    */
   enum TALER_MerchantConfirmationAlgorithm otp_algorithm;
 };
 
 
 /**
  * Typically called by `lookup_categories`.
  *
  * @param cls closure
  * @param category_id ID of the category
  * @param category_name name of the category
  * @param category_name_i18n translations of the @a category_name
  * @param product_count number of products in the category
  */
 typedef void
 (*TALER_MERCHANTDB_CategoriesCallback)(
   void *cls,
   uint64_t category_id,
   const char *category_name,
   const json_t *category_name_i18n,
   uint64_t product_count);
 
 
 /**
  * Typically called by `lookup_units`.
  *
  * @param cls closure
  * @param unit_serial database identifier
  * @param ud measurement unit details (borrowed)
  */
 typedef void
 (*TALER_MERCHANTDB_UnitsCallback)(
   void *cls,
   uint64_t unit_serial,
   const struct TALER_MERCHANTDB_UnitDetails *ud);
 
 
 /**
  * Details about a product category.
  */
 struct TALER_MERCHANTDB_CategoryDetails
 {
 
   /**
    * Name of the category.
    */
   char *category_name;
 
   /**
    * Translations of the name of the category.
    */
   json_t *category_name_i18n;
 
 };
 
 
 /**
  * Typically called by `lookup_webhooks`.
  *
  * @param cls a `json_t *` JSON array to build
  * @param webhook_id ID of the webhook
  * @param event_type event of the webhook
  */
 typedef void
 (*TALER_MERCHANTDB_WebhooksCallback)(
   void *cls,
   const char *webhook_id,
   const char *event_type);
 
 
 /**
  * Details about a webhook.
  */
 struct TALER_MERCHANTDB_WebhookDetails
 {
 
   /**
    * event of the webhook.
    */
   char *event_type;
 
   /**
    * URL of the webhook. The customer will be redirected on this url.
    */
   char *url;
 
   /**
    * Http method used by the webhook.
    */
   char *http_method;
 
   /**
    * Header template of the webhook.
    */
   char *header_template;
 
   /**
    * Body template of the webhook.
    */
   char *body_template;
 
 };
 
 
 /**
  * Typically called by `lookup_webhook_by_event`.
  *
  * @param cls a `json_t *` JSON array to build
  * @param webhook_serial reference to the configured webhook template.
  * @param event_type which type of event triggers this type of webhook
  * @param url the HTTP URL to make the webhook request to
  * @param http_method HTTP method use for the webhook
  * @param header_template template for the header of the webhook
  * @param body_template template for the body of the webhook
  */
 typedef void
 (*TALER_MERCHANTDB_WebhookDetailCallback)(
   void *cls,
   uint64_t webhook_serial,
   const char *event_type,
   const char *url,
   const char *http_method,
   const char *header_template,
   const char *body_template);
 
 
 /**
  * Typically called by `lookup_pending_webhooks`.
  *
  * @param cls a `json_t *` JSON array to build
  * @param webhook_pending_serial reference to the configured webhook template.
  * @param next_attempt is the time we should make the next request to the webhook.
  * @param retries how often have we tried this request to the webhook.
  * @param url to make request to
  * @param http_method use for the webhook
  * @param header of the webhook
  * @param body of the webhook
  */
 typedef void
 (*TALER_MERCHANTDB_PendingWebhooksCallback)(
   void *cls,
   uint64_t webhook_pending_serial,
   struct GNUNET_TIME_Absolute
   next_attempt,
   uint32_t retries,
   const char *url,
   const char *http_method,
   const char *header,
   const char *body);
 
 
 /**
  * Details about the pending webhook.
  */
 struct TALER_MERCHANTDB_PendingWebhookDetails
 {
 
   /**
    * Identifies when we should make the next request to the webhook. 0 for unknown,
    * #GNUNET_TIME_UNIT_FOREVER_ABS for never.
    */
   struct GNUNET_TIME_Absolute next_attempt;
 
   /**
    * How often have we tried this request so far.
    */
   uint32_t retries;
 
   /**
    * URL of the webhook. The customer will be redirected on this url.
    */
   char *url;
 
   /**
    * Http method used for the webhook.
    */
   char *http_method;
 
   /**
    * Header of the webhook.
    */
   char *header;
 
   /**
    * Body of the webhook.
    */
   char *body;
 
 };
 
 
 /**
  * Filter preferences.
  */
 struct TALER_MERCHANTDB_OrderFilter
 {
   /**
    * Filter orders by this fulfillment URL.
    */
   const char *fulfillment_url;
 
   /**
    * Filter orders by this session ID.
    */
   const char *session_id;
 
   /**
    * Filter by payment status.
    */
   enum TALER_EXCHANGE_YesNoAll paid;
 
   /**
    * Filter by refund status.
    */
   enum TALER_EXCHANGE_YesNoAll refunded;
 
   /**
    * Filter by wire transfer status.
    */
   enum TALER_EXCHANGE_YesNoAll wired;
 
   /**
    * Filter orders by date, exact meaning depends on @e delta.
    */
   struct GNUNET_TIME_Timestamp date;
 
   /**
    * Filter orders by order serial number, exact meaning depends on @e delta.
    */
   uint64_t start_row;
 
   /**
    * takes value of the form N (-N), so that at most N values strictly older
    * (younger) than start and date are returned.
    */
   int64_t delta;
 
   /**
    * Timeout for long-polling.
    */
   struct GNUNET_TIME_Relative timeout;
 
   /**
    * Filter to apply on the summary of the order.
    */
   const char *summary_filter;
 
 };
 
 
 /**
  * Typically called by `lookup_orders`.
  *
  * @param cls a `json_t *` JSON array to build
  * @param order_id ID of the order
  * @param order_serial row of the order in the database
  * @param timestamp creation time of the order in the database
  */
 typedef void
 (*TALER_MERCHANTDB_OrdersCallback)(void *cls,
                                    const char *order_id,
                                    uint64_t order_serial,
                                    struct GNUNET_TIME_Timestamp timestamp);
 
 
 /**
  * Typically called by `select_order_blinded_sigs`
  *
  * @param cls closure
  * @param hash hash of the token
  * @param blinded_sig blinded signature for the token
  */
 typedef void
 (*TALER_MERCHANTDB_BlindedSigCallback)(
   void *cls,
   struct GNUNET_HashCode *hash,
   struct GNUNET_CRYPTO_BlindedSignature *blinded_sig);
 
 /**
  * Function called with information about a coin that was deposited.
  *
  * @param cls closure
  * @param exchange_url exchange where @a coin_pub was deposited
  * @param coin_pub public key of the coin
  * @param amount_with_fee amount the exchange will deposit for this coin
  * @param deposit_fee fee the exchange will charge for this coin
  * @param refund_fee fee the exchange will charge for refunding this coin
  */
 typedef void
 (*TALER_MERCHANTDB_DepositsCallback)(
   void *cls,
   const char *exchange_url,
   const struct TALER_CoinSpendPublicKeyP *coin_pub,
   const struct TALER_Amount *amount_with_fee,
   const struct TALER_Amount *deposit_fee,
   const struct TALER_Amount *refund_fee);
 
 
 /**
  * Function called with information about a refund.
  *
  * @param cls closure
  * @param coin_pub public coin from which the refund comes from
  * @param refund_amount refund amount which is being taken from @a coin_pub
  */
 typedef void
 (*TALER_MERCHANTDB_RefundCallback)(
   void *cls,
   const struct TALER_CoinSpendPublicKeyP *coin_pub,
   const struct TALER_Amount *refund_amount);
 
 
 /**
  * Typically called by `lookup_transfer_details_by_order`.
  *
  * @param cls closure
  * @param wtid wire transfer subject of the wire transfer for the coin
  * @param exchange_url base URL of the exchange that made the payment
  * @param execution_time when was the payment made
  * @param deposit_value contribution of the coin to the total wire transfer value
  * @param deposit_fee deposit fee charged by the exchange for the coin
  * @param transfer_confirmed did the merchant confirm that a wire transfer with
  *        @a wtid over the total amount happened?
  * @param expected_credit_serial row of the expected wire transfer, usable
  *        as ``offset`` for the ``/private/incoming`` endpoint
  */
 typedef void
 (*TALER_MERCHANTDB_OrderTransferDetailsCallback)(
   void *cls,
   const struct TALER_WireTransferIdentifierRawP *wtid,
   const char *exchange_url,
   struct GNUNET_TIME_Timestamp execution_time,
   const struct TALER_Amount *deposit_value,
   const struct TALER_Amount *deposit_fee,
   bool transfer_confirmed,
   uint64_t expected_credit_serial);
 
 
 /**
  * Function called with detailed information about a refund.
  *
  * @param cls closure
  * @param refund_serial unique serial number of the refund
  * @param timestamp time of the refund (for grouping of refunds in the wallet UI)
  * @param coin_pub public coin from which the refund comes from
  * @param exchange_url URL of the exchange that issued @a coin_pub
  * @param rtransaction_id identificator of the refund
  * @param reason human-readable explanation of the refund
  * @param refund_amount refund amount which is being taken from @a coin_pub
  * @param pending true if the this refund was not yet processed by the wallet/exchange
  */
 typedef void
 (*TALER_MERCHANTDB_RefundDetailCallback)(
   void *cls,
   uint64_t refund_serial,
   struct GNUNET_TIME_Timestamp timestamp,
   const struct TALER_CoinSpendPublicKeyP *coin_pub,
   const char *exchange_url,
   uint64_t rtransaction_id,
   const char *reason,
   const struct TALER_Amount *refund_amount,
   bool pending);
 
 
 /**
  * Function called from ``account_kyc_get_status``
  * with KYC status information for this merchant.
  *
  * @param cls closure
  * @param h_wire hash of the wire account
  * @param payto_uri payto:// URI of the merchant's bank account
  * @param exchange_url base URL of the exchange for which this is a status
  * @param last_check when did we last get an update on our KYC status from the exchange
  * @param kyc_ok true if we satisfied the KYC requirements
  * @param access_token access token for the KYC SPA, NULL if we cannot access it yet (need KYC auth wire transfer)
  * @param last_http_status last HTTP status from /kyc-check
  * @param last_ec last Taler error code from /kyc-check
  * @param in_aml_review true if the account is pending review
  * @param jlimits JSON array of applicable AccountLimits, or NULL if unknown (like defaults apply)
  */
 typedef void
 (*TALER_MERCHANTDB_KycCallback)(
   void *cls,
   const struct TALER_MerchantWireHashP *h_wire,
   struct TALER_FullPayto payto_uri,
   const char *exchange_url,
   struct GNUNET_TIME_Timestamp last_check,
   bool kyc_ok,
   const struct TALER_AccountAccessTokenP *access_token,
   unsigned int last_http_status,
   enum TALER_ErrorCode last_ec,
   bool in_aml_review,
   const json_t *jlimits);
 
 
 /**
  * Function called from ``account_kyc_get_outdated``
  * with information about outdated KYC status information.
  *
  * @param cls closure
  * @param instance_id which instance is this about
  * @param exchange_url base URL of the exchange for which the status is dated
  * @param h_wire hash of the wire account for which the status is dated
  */
 typedef void
 (*TALER_MERCHANTDB_KycOutdatedCallback)(
   void *cls,
   const char *instance_id,
   const char *exchange_url,
   const struct TALER_MerchantWireHashP *h_wire);
 
 
 /**
  * Function called about the ``/keys`` status of every exchange
  * we are working with.
  *
  * @param cls closure
  * @param exchange_url base URL of the exchange
  * @param next_download when will be the next download
  * @param keys_expiration when does the current ``/keys`` response expire
  * @param http_status last HTTP status from ``/keys``
  * @param ec last error code from fetching ``/keys``
  */
 typedef void
 (*TALER_MERCHANTDB_ExchangesCallback)(
   void *cls,
   const char *exchange_url,
   struct GNUNET_TIME_Absolute next_download,
   struct GNUNET_TIME_Absolute keys_expiration,
   unsigned int http_status,
   enum TALER_ErrorCode ec);
 
 /**
  * Results from trying to increase a refund.
  */
 enum TALER_MERCHANTDB_RefundStatus
 {
 
   /**
    * Refund amount exceeds legal exchange limits.
    */
   TALER_MERCHANTDB_RS_LEGAL_FAILURE = -5,
 
   /**
    * Refund amount currency does not match original payment.
    */
   TALER_MERCHANTDB_RS_BAD_CURRENCY = -4,
 
   /**
    * Refund amount exceeds original payment.
    */
   TALER_MERCHANTDB_RS_TOO_HIGH = -3,
 
   /**
    * Hard database failure.
    */
   TALER_MERCHANTDB_RS_HARD_ERROR = -2,
 
   /**
    * Soft database failure.
    */
   TALER_MERCHANTDB_RS_SOFT_ERROR = -1,
 
   /**
    * Order not found.
    */
   TALER_MERCHANTDB_RS_NO_SUCH_ORDER = 0,
 
   /**
    * Refund is now at or above the requested amount.
    */
   TALER_MERCHANTDB_RS_SUCCESS = 1
 
 };
 
 
 /**
  * Function called with information about a wire transfer identifier.
  *
  * @param cls closure
  * @param order_id the order to which the deposits belong
  * @param deposit_value the amount deposited under @a order_id
  * @param deposit_fee the fee charged for @a deposit_value
  */
 typedef void
 (*TALER_MERCHANTDB_TransferSummaryCallback)(
   void *cls,
   const char *order_id,
   const struct TALER_Amount *deposit_value,
   const struct TALER_Amount *deposit_fee);
 
 
 /**
  * Function called with information about wire transfers
  * that taler-merchant-exchange still needs to process.
  *
  * @param cls closure
  * @param rowid row of the transfer in the merchant database
  * @param instance_id instance that received the transfer
  * @param exchange_url URL of the exchange that is making the deposit
  * @param payto_uri account of the merchant that received the transfer
  * @param wtid wire transfer subject identifying the aggregation
  * @param next_attempt when should we next try to interact with the exchange
  */
 typedef void
 (*TALER_MERCHANTDB_OpenTransferCallback)(
   void *cls,
   uint64_t rowid,
   const char *instance_id,
   const char *exchange_url,
   struct TALER_FullPayto payto_uri,
   const struct TALER_WireTransferIdentifierRawP *wtid,
   struct GNUNET_TIME_Absolute next_attempt);
 
 
 /**
  * Callback for results from `lookup_pending_deposits`.
  *
  * @param cls NULL
  * @param deposit_serial identifies the deposit operation
  * @param wire_deadline when is the wire due
  * @param retry_time when to next try the exchange again
  * @param h_contract_terms hash of the contract terms
  * @param merchant_priv private key of the merchant
  * @param instance_id name of the instance
  * @param h_wire hash of the merchant's wire account into
  * @param amount_with_fee amount the exchange will deposit for this coin
  * @param deposit_fee fee the exchange will charge for this coin which the deposit was made
  * @param coin_pub public key of the deposited coin
  */
 typedef void
 (*TALER_MERCHANTDB_PendingDepositsCallback) (
   void *cls,
   uint64_t deposit_serial,
   struct GNUNET_TIME_Absolute wire_deadline,
   struct GNUNET_TIME_Absolute retry_time,
   const struct TALER_PrivateContractHashP *h_contract_terms,
   const struct TALER_MerchantPrivateKeyP *merchant_priv,
   const char *instance_id,
   const struct TALER_MerchantWireHashP *h_wire,
   const struct TALER_Amount *amount_with_fee,
   const struct TALER_Amount *deposit_fee,
   const struct TALER_CoinSpendPublicKeyP *coin_pub);
 
 
 /**
  * Function called with detailed information about a wire transfer and
  * the underlying deposits that are being aggregated.
  *
  * @param cls closure
  * @param current_offset offset in the exchange reply we are at
  * @param ttd details about the transfer at @a current_offset
  */
 typedef void
 (*TALER_MERCHANTDB_TransferDetailsCallback)(
   void *cls,
   unsigned int current_offset,
   const struct TALER_TrackTransferDetails *ttd);
 
 
 /**
  * Function called with information about a accounts
  * the wirewatcher should monitor.
  *
  * @param cls closure
  * @param instance instance that owns the account
  * @param payto_uri account URI
  * @param credit_facade_url URL for the credit facade
  * @param credit_facade_credentials account access credentials
  * @param last_serial last transaction serial (inclusive) we have seen from this account
  */
 typedef void
 (*TALER_MERCHANTDB_WirewatchWorkCallback)(
   void *cls,
   const char *instance,
   struct TALER_FullPayto payto_uri,
   const char *credit_facade_url,
   const json_t *credit_facade_credentials,
   uint64_t last_serial);
 
 
 /**
  * Function called with information about a wire transfer.
  *
  * @param cls closure with a `json_t *` array to build up the response
  * @param expected_credit_amount how we expect to see wired to the merchant (minus fees), NULL if unknown
  * @param wtid wire transfer identifier
  * @param payto_uri target account that received the wire transfer
  * @param exchange_url base URL of the exchange that made the wire transfer
  * @param transfer_serial_id serial number identifying the transfer in the backend
  * @param expected_transfer_serial_id serial number identifying the expected transfer in the backend, 0 if not @a expected
  * @param execution_time when did the exchange make the transfer, #GNUNET_TIME_UNIT_FOREVER_ABS
  *           if it did not yet happen
  * @param expected true if the merchant acknowledged the wire transfer reception
  */
 typedef void
 (*TALER_MERCHANTDB_TransferCallback)(
   void *cls,
   const struct TALER_Amount *expected_credit_amount,
   const struct TALER_WireTransferIdentifierRawP *wtid,
   struct TALER_FullPayto payto_uri,
   const char *exchange_url,
   uint64_t transfer_serial_id,
   uint64_t expected_transfer_serial_id,
   struct GNUNET_TIME_Absolute execution_time,
   bool expected);
 
 
 /**
  * Function called with information about expected incoming wire transfers.
  *
  * @param cls closure with a `json_t *` array to build up the response
  * @param expected_credit_amount how we expect to see wired to the merchant (minus fees), NULL if unknown
  * @param wtid wire transfer identifier
  * @param payto_uri target account that received the wire transfer
  * @param exchange_url base URL of the exchange that made the wire transfer
  * @param expected_transfer_serial_id serial number identifying the expected transfer in the backend
  * @param execution_time when did the exchange claim to have made the transfer
  * @param confirmed true if the merchant confirmed this wire transfer
  *                 false if it is so far only claimed to have been made by the exchange
  * @param validated true if the reconciliation succeeded
  * @param last_http_status HTTP status of our last request to the exchange for this transfer
  * @param last_ec last error code we got back (otherwise #TALER_EC_NONE)
  * @param last_error_detail last detail we got back (or NULL for none)
  */
 typedef void
 (*TALER_MERCHANTDB_IncomingCallback)(
   void *cls,
   const struct TALER_Amount *expected_credit_amount,
   const struct TALER_WireTransferIdentifierRawP *wtid,
   struct TALER_FullPayto payto_uri,
   const char *exchange_url,
   uint64_t expected_transfer_serial_id,
   struct GNUNET_TIME_Timestamp execution_time,
   bool confirmed,
   bool validated,
   unsigned int last_http_status,
   enum TALER_ErrorCode last_ec,
   const char *last_error_detail);
 
 
 /**
  * If the given account is feasible, add it to the array
  * of accounts we return.
  *
  * @param cls closure
  * @param payto_uri URI of the account
  * @param conversion_url URL of a conversion service
  * @param debit_restrictions restrictions for debits from account
  * @param credit_restrictions restrictions for credits to account
  * @param master_sig signature affirming the account
  */
 typedef void
 (*TALER_MERCHANTDB_ExchangeAccountCallback) (
   void *cls,
   struct TALER_FullPayto payto_uri,
   const char *conversion_url,
   const json_t *debit_restrictions,
   const json_t *credit_restrictions,
   const struct TALER_MasterSignatureP *master_sig);
 
 
 /**
  * Function called with information about a coin that was deposited.
  *
  * @param cls closure
  * @param deposit_serial which deposit operation is this about
  * @param exchange_url URL of the exchange that issued the coin
  * @param h_wire hash of merchant's wire details
  * @param deposit_timestamp when was the deposit made
  * @param amount_with_fee amount the exchange will deposit for this coin
  * @param deposit_fee fee the exchange will charge for this coin
  * @param coin_pub public key of the coin
  */
 typedef void
 (*TALER_MERCHANTDB_DepositedCoinsCallback)(
   void *cls,
   uint64_t deposit_serial,
   const char *exchange_url,
   const struct TALER_MerchantWireHashP *h_wire,
   struct GNUNET_TIME_Timestamp deposit_timestamp,
   const struct TALER_Amount *amount_with_fee,
   const struct TALER_Amount *deposit_fee,
   const struct TALER_CoinSpendPublicKeyP *coin_pub);
 
 
 /**
  * Function called with information about a coin that was deposited.
  *
  * @param cls closure
  * @param exchange_url URL of the exchange that issued the coin
  * @param amount_with_fee amount the exchange will deposit for this coin
  * @param deposit_fee fee the exchange will charge for this coin
  * @param refund_fee fee the exchange will charge for refunding this coin
  * @param wire_fee wire fee the exchange charges
  * @param h_wire hash of merchant's wire details
  * @param deposit_timestamp when did the exchange receive the deposit
  * @param refund_deadline until when are refunds allowed
  * @param exchange_sig signature by the exchange
  * @param exchange_pub exchange signing key used for @a exchange_sig
  */
 typedef void
 (*TALER_MERCHANTDB_CoinDepositCallback)(
   void *cls,
   const char *exchange_url,
   const struct TALER_Amount *amount_with_fee,
   const struct TALER_Amount *deposit_fee,
   const struct TALER_Amount *refund_fee,
   const struct TALER_Amount *wire_fee,
   const struct TALER_MerchantWireHashP *h_wire,
   struct GNUNET_TIME_Timestamp deposit_timestamp,
   struct GNUNET_TIME_Timestamp refund_deadline,
   const struct TALER_ExchangeSignatureP *exchange_sig,
   const struct TALER_ExchangePublicKeyP *exchange_pub);
 
 
 /**
  * Possible token family kinds.
  */
 enum TALER_MERCHANTDB_TokenFamilyKind
 {
 
   /**
    * Token family representing a discount token
    */
   TALER_MERCHANTDB_TFK_Discount = 0,
 
   /**
    * Token family representing a subscription token
    */
   TALER_MERCHANTDB_TFK_Subscription = 1,
 
 };
 
 
 /**
  * Typically called by `lookup_token_families`.
  *
  * @param cls closure
  * @param slug slug of the token family
  * @param name name of the token family
  * @param description description of the token family
  * @param description_i18n Internationalized token family description.
  * @param start_time start time of the token family's validity period
  * @param expiration end time of the token family's validity period
  * @param kind kind of the token family
  */
 typedef void
 (*TALER_MERCHANTDB_TokenFamiliesCallback)(
   void *cls,
   const char *slug,
   const char *name,
   const char *description,
   const json_t *description_i18n,
   struct GNUNET_TIME_Timestamp start_time,
   struct GNUNET_TIME_Timestamp expiration,
   const char *kind);
 
 
 /**
  * Typically called by `select_money_pots`.
  *
  * @param cls closure
  * @param name set to name of the pot
  * @param pot_total_len length of @a pot_totals array
  * @param pot_totals amounts currently in the pot
  */
 typedef void
 (*TALER_MERCHANTDB_MoneyPotsCallback)(
   void *cls,
   uint64_t money_pot_id,
   const char *name,
   size_t pot_total_len,
   const struct TALER_Amount *pot_totals);
 
 
 /**
  * Typically called by `select_reports`.
  *
  * @param cls closure
  * @param name name of the report
  * @param description description of the report
  * @param frequency the report frequency
  */
 typedef void
 (*TALER_MERCHANTDB_ReportsCallback)(
   void *cls,
   uint64_t report_id,
   const char *report_description,
   struct GNUNET_TIME_Relative frequency);
 
 
 /**
  * Typically called by `lookup_reports_pending`.
  *
  * @param cls closure
  * @param instance_id name of the instance
  * @param report_id serial number of the report
  * @param report_program_section configuration section of program
  *   for report generation
  * @param report_description text describing the report
  * @param mime_type mime type to request
  * @param report_token token to authorize access to the data source
  * @param target_address where to send report data
  * @param frequency report frequency
  * @param frequency_shift how much to shift the report time from a
  *   multiple of the report @a frequency
  * @param next_transmission when is the next transmission of this report
  *   due
  * @param one_shot true if the report should be removed from the
  *   list after generation instead of being repeated
  */
 typedef void
 (*TALER_MERCHANTDB_ReportsPendingCallback)(
   void *cls,
   const char *instance_id,
   uint64_t report_id,
   const char *report_program_section,
   const char *report_description,
   const char *mime_type,
   const struct TALER_MERCHANT_ReportToken *report_token,
   const char *target_address,
   struct GNUNET_TIME_Relative frequency,
   struct GNUNET_TIME_Relative frequency_shift,
   struct GNUNET_TIME_Absolute next_transmission,
   bool one_shot);
 
 
 /**
  * Typically called by `select_product_groups`.
  *
  * @param cls closure
  * @param product_group_id ID of the product group
  * @param group_name set to name of the group
  * @param group_description set to description of the group
  */
 typedef void
 (*TALER_MERCHANTDB_ProductGroupsCallback)(
   void *cls,
   uint64_t product_group_id,
   const char *group_name,
   const char *group_description);
 
 
 /**
  * Details about a token family.
  */
 struct TALER_MERCHANTDB_TokenFamilyDetails
 {
   /**
    * Token family slug used for identification.
    */
   char *slug;
 
   /**
    * User readable name of the token family.
    */
   char *name;
 
   /**
    * Description of the token family.
    */
   char *description;
 
   /**
    * Internationalized token family description.
    */
   json_t *description_i18n;
 
   /**
    * Meta-data associated with the token family.
    * Includes information like "trusted_domains" or
    * "expected_domains", if set.
    */
   json_t *extra_data;
 
   /**
    * Cipher that should be used for this token family.  Note: We do not expose
    * this over the API and do not let clients set it. NULL for default (when
    * calling database).
    */
   char *cipher_spec;
 
   /**
    * Start time of the token family duration.
    */
   struct GNUNET_TIME_Timestamp valid_after;
 
   /**
    * End time of the token family duration.
    */
   struct GNUNET_TIME_Timestamp valid_before;
 
   /**
    * Validity duration of the token family. Must be larger or
    * equal to @a rounding plus @a start_offset_s.
    */
   struct GNUNET_TIME_Relative duration;
 
   /**
    * Rounding duration of the token family.
    */
   struct GNUNET_TIME_Relative validity_granularity;
 
   /**
    * Offset (in seconds) to subtract from the rounded
    * validity start period.
    */
   struct GNUNET_TIME_Relative start_offset;
 
   /**
    * Token family kind.
    */
   enum TALER_MERCHANTDB_TokenFamilyKind kind;
 
   /**
    * Counter for each issued token of this family.
    */
   uint64_t issued;
 
   /**
    * Counter for each used token of this family.
    */
   uint64_t used;
 };
 
 
 /**
  * Details about a token key.
  */
 struct TALER_MERCHANTDB_TokenFamilyKeyDetails
 {
   /**
    * Tokens signed with this key are valid from this date on.
    * This is the time the key was created.
    */
   struct GNUNET_TIME_Timestamp signature_validity_start; // valid_after;
 
   /**
    * Tokens signed with this key are valid until this date.
    */
   struct GNUNET_TIME_Timestamp signature_validity_end; // valid_before;
 
   /**
    * Private key expires for use at this time. Signatures can
    * only be created until this point.
    */
   struct GNUNET_TIME_Timestamp private_key_deleted_at;
 
   /**
    * Token family public key.
    */
   struct TALER_TokenIssuePublicKey pub;
 
   /**
    * Token family private key.
    */
   struct TALER_TokenIssuePrivateKey priv;
 
   /**
    * Details about the token family this key belongs to.
    */
   struct TALER_MERCHANTDB_TokenFamilyDetails token_family;
 };
 
 
 /**
  * Function called with applicable token keys.
  *
  * @param cls closure
  * @param details details about an applicable key
  */
 typedef void
 (*TALER_MERCHANTDB_TokenKeyCallback) (
   void *cls,
   const struct TALER_MERCHANTDB_TokenFamilyKeyDetails *details);
 
 
 /**
  * Details about a spent token.
  */
 struct TALER_MERCHANTDB_SpentTokenDetails
 {
   /**
    * Public key of the spent token.
    */
   struct TALER_TokenUsePublicKeyP pub;
 
   /**
    * Signature that this token was spent on the specified order.
    */
   struct TALER_TokenUseSignatureP sig;
 
   /**
    * Blind signature for the spent token to prove validity of it.
    */
   struct TALER_BlindedTokenIssueSignature blind_sig;
 };
 
 
 /**
  * Function called with information about a token that was used.
  *
  * @param cls closure
  * @param spent_token_serial which used token is this about
  * @param h_contract_terms hash of the contract terms this token was used on
  * @param h_issue_pub hash of the token issue public key
  * @param use_pub token use public key
  * @param use_sig token use signature
  * @param issue_sig unblinded token issue signature
  */
 typedef void
 (*TALER_MERCHANTDB_UsedTokensCallback)(
   void *cls,
   uint64_t spent_token_serial,
   const struct TALER_PrivateContractHashP *h_contract_terms,
   const struct TALER_TokenIssuePublicKeyHashP *h_issue_pub,
   const struct TALER_TokenUsePublicKeyP *use_pub,
   const struct TALER_TokenUseSignatureP *use_sig,
   const struct TALER_TokenIssueSignature *issue_sig);
 
 
 /**
  * Returns amount-valued statistics by bucket.
  * Called by `lookup_statistics_amount_by_bucket`.
  *
  * @param cls closure
  * @param description description of the statistic
  * @param bucket_start start time of the bucket
  * @param bucket_end end time of the bucket
  * @param bucket_range range of the bucket
  * @param cumulative_amounts_len the length of @a cumulative_amounts
  * @param cumulative_amounts the cumulative amounts array
  */
 typedef void
 (*TALER_MERCHANTDB_AmountByBucketStatisticsCallback)(
   void *cls,
   const char *description,
   struct GNUNET_TIME_Timestamp bucket_start,
   struct GNUNET_TIME_Timestamp bucket_end,
   const char *bucket_range,
   unsigned int cumulative_amounts_len,
   const struct TALER_Amount cumulative_amounts[static cumulative_amounts_len]);
 
 
 /**
  * Returns amount-valued statistics by bucket.
  * Called by `lookup_statistics_amount_by_bucket2`.
  *
  * @param cls closure
  * @param bucket_start start time of the bucket
  * @param cumulative_amounts_len the length of @a cumulative_amounts
  * @param cumulative_amounts the cumulative amounts array
  */
 typedef void
 (*TALER_MERCHANTDB_AmountByBucketStatisticsCallback2)(
   void *cls,
   struct GNUNET_TIME_Timestamp bucket_start,
   unsigned int cumulative_amounts_len,
   const struct TALER_Amount cumulative_amounts[static cumulative_amounts_len]);
 
 
 /**
  * Returns amount-valued statistics over a particular time interval.
  * Called by `lookup_statistics_amount_by_interval`.
  *
  * @param cls closure
  * @param description description of the statistic
  * @param interval_start start time of the bucket
  * @param cumulative_amounts_len the length of @a cumulative_amounts
  * @param cumulative_amounts the cumulative amounts array
  */
 typedef void
 (*TALER_MERCHANTDB_AmountByIntervalStatisticsCallback)(
   void *cls,
   const char *description,
   struct GNUNET_TIME_Timestamp interval_start,
   unsigned int cumulative_amounts_len,
   const struct TALER_Amount cumulative_amounts[static cumulative_amounts_len]);
 
 
 /**
  * Function returning integer-valued statistics for a bucket.
  * Called by `lookup_statistics_counter_by_bucket`.
  *
  * @param cls closure
  * @param description description of the statistic
  * @param bucket_start start time of the bucket
  * @param bucket_end end time of the bucket
  * @param bucket_range range of the bucket
  * @param cumulative_counter counter value
  */
 typedef void
 (*TALER_MERCHANTDB_CounterByBucketStatisticsCallback)(
   void *cls,
   const char *description,
   struct GNUNET_TIME_Timestamp bucket_start,
   struct GNUNET_TIME_Timestamp bucket_end,
   const char *bucket_range,
   uint64_t cumulative_counter);
 
 
 /**
  * Function returning reconciliation details for an
  * expected incoming wire transfer.
  * Called by `lookup_reconciliation_details`.
  *
  * @param cls closure
  * @param order_id order that was paid and then aggregated
  * @param remaining_deposit deposited amount minus any refunds
  * @param deposit_fee deposit fees paid to the exchange for the order
  */
 typedef void
 (*TALER_MERCHANTDB_ReconciliationDetailsCallback)(
   void *cls,
   const char *order_id,
   const struct TALER_Amount *remaining_deposit,
   const struct TALER_Amount *deposit_fee);
 
 
 /**
  * Details about a statistic with counter.
  */
 struct TALER_MERCHANTDB_StatisticsCounterByBucketDetails
 {
   /**
    * Start time of the bucket (inclusive).
    */
   struct GNUNET_TIME_Timestamp start_time;
 
   /**
    * End time of the bucket (exclusive).
    */
   struct GNUNET_TIME_Timestamp end_time;
 
   /**
    * Description of the statistic
    */
   char*description;
 
   /**
    * Range of the bucket
    */
   char *range;
 
   /**
    * Sum of all counters falling under the given
    * SLUG within this timeframe
    */
   uint64_t cumulative_number;
 };
 
 /**
  * Details about a statistic with counter.
  */
 struct TALER_MERCHANTDB_StatisticsCounterByIntervalDetails
 {
   /**
    * Start time of the interval.
    * The interval always ends at the response generation time.
    */
   struct GNUNET_TIME_Timestamp start_time;
 
   /**
    * Sum of all counters falling under the given
    * SLUG within this timeframe
    */
   uint64_t cumulative_counter;
 };
 
 
 /**
  * Function returning integer-valued statistics for a time interval.
  * Called by `lookup_statistics_counter_by_interval`.
  *
  * @param cls closure
  * @param description description of the statistic
  * @param interval_start start time of the interval
  * @param cumulative_counter counter value
  */
 typedef void
 (*TALER_MERCHANTDB_CounterByIntervalStatisticsCallback)(
   void *cls,
   const char *description,
   struct GNUNET_TIME_Timestamp interval_start,
   uint64_t cumulative_counter);
 
 
 /**
  * Function returning integer-valued statistics for a bucket.
  * Called by `lookup_statistics_counter_by_bucket2`.
  *
  * @param cls closure
  * @param bucket_start start time of the bucket
  * @param counters_len the length of @a cumulative_amounts
  * @param descriptions description for the counter in the bucket
  * @param counters the counters in the bucket
  */
 typedef void
 (*TALER_MERCHANTDB_CounterByBucketStatisticsCallback2)(
   void *cls,
   struct GNUNET_TIME_Timestamp bucket_start,
   unsigned int counters_len,
   const char *descriptions[static counters_len],
   uint64_t counters[static counters_len]);
 
 
 /**
  * Handle to interact with the database.
  *
  * Functions ending with "_TR" run their OWN transaction scope
  * and MUST NOT be called from within a transaction setup by the
  * caller.  Functions ending with "_NT" require the caller to
  * setup a transaction scope.  Functions without a suffix are
  * simple, single SQL queries that MAY be used either way.
  */
 struct TALER_MERCHANTDB_Plugin
 {
 
   /**
    * Closure for all callbacks.
    */
   void *cls;
 
   /**
    * Name of the library which generated this plugin.  Set by the
    * plugin loader.
    */
   char *library_name;
 
   /**
    * Connect to the database.
    *
    * @param cls closure
    */
   enum GNUNET_GenericReturnValue
     (*connect)(void *cls);
 
   /**
    * Drop merchant tables. Used for testcases and to reset the DB.
    *
    * @param cls closure
    * @return #GNUNET_OK upon success; #GNUNET_SYSERR upon failure
    */
   enum GNUNET_GenericReturnValue
     (*drop_tables)(void *cls);
 
   /**
    * Garbage collect database. Removes unnecessary data.
    *
    * @param cls closure
    * @return #GNUNET_OK upon success; #GNUNET_SYSERR upon failure
    */
   enum GNUNET_GenericReturnValue
     (*gc)(void *cls);
 
   /**
    * Initialize merchant tables
    *
    * @param cls closure
    * @return #GNUNET_OK upon success; #GNUNET_SYSERR upon failure
    */
   enum GNUNET_GenericReturnValue
     (*create_tables)(void *cls);
 
   /**
    * Register callback to be invoked on events of type @a es.
    *
    * @param cls database context to use
    * @param es specification of the event to listen for
    * @param timeout how long to wait for the event
    * @param cb function to call when the event happens, possibly
    *         multiple times (until cancel is invoked)
    * @param cb_cls closure for @a cb
    * @return handle useful to cancel the listener
    */
   struct GNUNET_DB_EventHandler *
   (*event_listen)(void *cls,
                   const struct GNUNET_DB_EventHeaderP *es,
                   struct GNUNET_TIME_Relative timeout,
                   GNUNET_DB_EventCallback cb,
                   void *cb_cls);
 
   /**
    * Stop notifications.
    *
    * @param eh handle to unregister.
    */
   void
   (*event_listen_cancel)(struct GNUNET_DB_EventHandler *eh);
 
 
   /**
    * Notify all that listen on @a es of an event.
    *
    * @param cls database context to use
    * @param es specification of the event to generate
    * @param extra additional event data provided
    * @param extra_size number of bytes in @a extra
    */
   void
   (*event_notify)(void *cls,
                   const struct GNUNET_DB_EventHeaderP *es,
                   const void *extra,
                   size_t extra_size);
 
 
   /**
    * Do a pre-flight check that we are not in an uncommitted transaction.  If
    * we are, die.  Does not return anything, as we will continue regardless of
    * the outcome.
    *
    * @param cls the `struct PostgresClosure` with the plugin-specific state
    */
   void
   (*preflight) (void *cls);
 
   /**
    * Start a transaction.
    *
    * @param cls the `struct PostgresClosure` with the plugin-specific state
    * @param name unique name identifying the transaction (for debugging),
    *             must point to a constant
    * @return #GNUNET_OK on success
    */
   enum GNUNET_GenericReturnValue
     (*start)(void *cls,
              const char *name);
 
   /**
    * Start a transaction with isolation level 'read committed'.
    *
    * @param cls the `struct PostgresClosure` with the plugin-specific state
    * @param name unique name identifying the transaction (for debugging),
    *             must point to a constant
    * @return #GNUNET_OK on success
    */
   enum GNUNET_GenericReturnValue
     (*start_read_committed)(void *cls,
                             const char *name);
 
   /**
    * Roll back the current transaction of a database connection.
    *
    * @param cls the `struct PostgresClosure` with the plugin-specific state
    */
   void
   (*rollback) (void *cls);
 
   /**
    * Commit the current transaction of a database connection.
    *
    * @param cls the `struct PostgresClosure` with the plugin-specific state
    * @return transaction status
    */
   enum GNUNET_DB_QueryStatus
     (*commit)(void *cls);
 
   /**
    * Lookup all of the instances this backend has configured.
    *
    * @param cls closure
    * @param active_only only find 'active' instances
    * @param cb function to call on all instances found
    * @param cb_cls closure for @a cb
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_instances)(void *cls,
                         bool active_only,
                         TALER_MERCHANTDB_InstanceCallback cb,
                         void *cb_cls);
 
   /**
    * Lookup one of the instances this backend has configured.
    *
    * @param cls closure
    * @param id ID of instance to look up
    * @param active_only only find 'active' instances
    * @param cb function to call on all instances found
    * @param cb_cls closure for @a cb
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_instance)(void *cls,
                        const char *id,
                        bool active_only,
                        TALER_MERCHANTDB_InstanceCallback cb,
                        void *cb_cls);
 
   /**
    * Lookup authentication data of an instance.
    *
    * @param cls closure
    * @param instance_id instance to query
    * @param[out] ias where to store the auth data
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_instance_auth)(void *cls,
                             const char *instance_id,
                             struct TALER_MERCHANTDB_InstanceAuthSettings *ias);
 
 
   /**
    * Insert information about an instance into our database.
    *
    * @param cls closure
    * @param merchant_pub public key of the instance
    * @param merchant_priv private key of the instance
    * @param is details about the instance
    * @param validation_needed true if validation is
    *        required before the instance can be used
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*insert_instance)(void *cls,
                        const struct TALER_MerchantPublicKeyP *merchant_pub,
                        const struct TALER_MerchantPrivateKeyP *merchant_priv,
                        const struct TALER_MERCHANTDB_InstanceSettings *is,
                        const struct TALER_MERCHANTDB_InstanceAuthSettings *ias,
                        bool validation_needed);
 
 
   /**
    * Insert information about an instance's account into our database.
    *
    * @param cls closure
    * @param account_details details about the account
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*insert_account)(
     void *cls,
     const struct TALER_MERCHANTDB_AccountDetails *account_details);
 
 
   /**
    * Insert instance login token into our database.
    *
    * @param cls closure
    * @param id identifier of the instance
    * @param token value of the token
    * @param creation_time the current time
    * @param expiration_time when does the token expire
    * @param validity_scope scope of the token
    * @param description description of the token
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*insert_login_token)(
     void *cls,
     const char *id,
     const struct TALER_MERCHANTDB_LoginTokenP *token,
     struct GNUNET_TIME_Timestamp creation_time,
     struct GNUNET_TIME_Timestamp expiration_time,
     uint32_t validity_scope,
     const char *description);
 
 
   /**
    * Lookup information about a login token from database.
    *
    * @param cls closure
    * @param id identifier of the instance
    * @param token value of the token
    * @param[out] expiration_time set to expiration time
    * @param[out] validity_scope set to scope of the token
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*select_login_token)(
     void *cls,
     const char *id,
     const struct TALER_MERCHANTDB_LoginTokenP *token,
     struct GNUNET_TIME_Timestamp *expiration_time,
     uint32_t *validity_scope);
 
   /**
    * Lookup login tokens for instance.
    *
    * @param cls closure
    * @param instance_id instance to lookup tokens for
    * @param offset transfer_serial number of the transfer we want to offset from
    * @param limit number of entries to return, negative for descending,
    *                positive for ascending
    * @param cb function to call on all products found
    * @param cb_cls closure for @a cb
    * @return database result code
     */
   enum GNUNET_DB_QueryStatus
     (*lookup_login_tokens)(void *cls,
                            const char *instance_id,
                            uint64_t offset,
                            int64_t limit,
                            TALER_MERCHANTDB_LoginTokensCallback cb,
                            void *cb_cls);
 
   /**
    * Delete login token from database.
    *
    * @param cls closure
    * @param id identifier of the instance
    * @param token value of the token
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*delete_login_token)(
     void *cls,
     const char *id,
     const struct TALER_MERCHANTDB_LoginTokenP *token);
 
   /**
    * Delete login token from database by serial.
    *
    * @param cls closure
    * @param id identifier of the instance
    * @param serial serial of the token
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*delete_login_token_serial)(
     void *cls,
     const char *id,
     uint64_t serial);
 
 
   /**
    * Update information about an instance's account into our database.
    *
    * @param cls closure
    * @param id identifier of the instance
    * @param h_wire which account to update
    * @param extra_wire_subject_metadata additional metadata to include in wire transfer subjects
    * @param credit_facade_url new facade URL, can be NULL
    * @param credit_facade_credentials new credentials, can be NULL
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*update_account)(
     void *cls,
     const char *id,
     const struct TALER_MerchantWireHashP *h_wire,
     const char *extra_wire_subject_metadata,
     const char *credit_facade_url,
     const json_t *credit_facade_credentials);
 
 
   /**
    * Obtain information about an instance's accounts.
    *
    * @param cls closure
    * @param id identifier of the instance
    * @param cb function to call on each account
    * @param cb_cls closure for @a cb
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*select_accounts)(
     void *cls,
     const char *id,
     TALER_MERCHANTDB_AccountCallback cb,
     void *cb_cls);
 
 
   /**
    * Obtain detailed information about an instance's account.
    *
    * @param cls closure
    * @param id identifier of the instance
    * @param h_wire wire hash of the account
    * @param[out] ad account details returned
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*select_account)(
     void *cls,
     const char *id,
     const struct TALER_MerchantWireHashP *h_wire,
     struct TALER_MERCHANTDB_AccountDetails *ad);
 
 
   /**
  * Obtain detailed information about an instance's account.
  *
  * @param cls closure
  * @param id identifier of the instance
  * @param payto_uri URI of the account
  * @param[out] ad account details returned
  * @return database result code
  */
   enum GNUNET_DB_QueryStatus
     (*select_account_by_uri)(
     void *cls,
     const char *id,
     struct TALER_FullPayto payto_uri,
     struct TALER_MERCHANTDB_AccountDetails *ad);
 
 
   /**
    * Delete private key of an instance from our database.
    *
    * @param cls closure
    * @param merchant_id identifier of the instance
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*delete_instance_private_key)(
     void *cls,
     const char *merchant_id);
 
   /**
    * Purge an instance and all associated information from our database.
    * Highly likely to cause undesired data loss. Use with caution.
    *
    * @param cls closure
    * @param merchant_id identifier of the instance
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*purge_instance)(void *cls,
                       const char *merchant_id);
 
   /**
    * Update information about an instance into our database.
    *
    * @param cls closure
    * @param is details about the instance
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*update_instance)(void *cls,
                        const struct TALER_MERCHANTDB_InstanceSettings *is);
 
   /**
    * Update information about an instance's authentication settings
    * into our database.
    *
    * @param cls closure
    * @param merchant_id merchant backend instance ID
    * @param ias instance auth settings
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*update_instance_auth)(
     void *cls,
     const char *merchant_id,
     const struct TALER_MERCHANTDB_InstanceAuthSettings *ias);
 
   /**
    * Set an instance's account in our database to "inactive".
    *
    * @param cls closure
    * @param merchant_id merchant backend instance ID
    * @param h_wire hash of the wire account to set to inactive
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*inactivate_account)(void *cls,
                           const char *merchant_id,
                           const struct TALER_MerchantWireHashP *h_wire);
 
 
   /**
    * Set an instance's account in our database to "active".
    *
    * @param cls closure
    * @param account_details details of the account to actiate
    * @param[out] h_wire set to the hash of the salted payto URI
    * @param[out] salt set to salt used for computing @a h_wire
    * @param[out] not_found set to true if the instance was not found
    * @param[out] conflict set to true if a conflicting account is active
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*activate_account)(
     void *cls,
     const struct TALER_MERCHANTDB_AccountDetails *account_details,
     struct TALER_MerchantWireHashP *h_wire,
     struct TALER_WireSaltP *salt,
     bool *not_found,
     bool *conflict);
 
 
   /**
    * Check an instance's account's KYC status. Triggers
    * a request to taler-merchant-kyccheck to get a
    * KYC status update as a side-effect!
    *
    * @param cls closure
    * @param merchant_id merchant backend instance ID
    * @param h_wire hash of the wire account to check,
    *        NULL to check all accounts of the merchant
    * @param exchange_url base URL of the exchange to check,
    *        NULL to check all exchanges
    * @param kyc_cb KYC status callback to invoke
    * @param kyc_cb_cls closure for @a kyc_cb
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*account_kyc_get_status)(
     void *cls,
     const char *merchant_id,
     const struct TALER_MerchantWireHashP *h_wire,
     const char *exchange_url,
     TALER_MERCHANTDB_KycCallback kyc_cb,
     void *kyc_cb_cls);
 
 
   /**
    * Find accounts requiring KYC checks.
    *
    * @param cls closure
    * @param kyc_cb status callback to invoke
    * @param kyc_cb_cls closure for @a kyc_cb
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*account_kyc_get_outdated)(
     void *cls,
     TALER_MERCHANTDB_KycOutdatedCallback kyc_cb,
     void *kyc_cb_cls);
 
 
   /**
    * Check an account's KYC status at an exchange.
    *
    * @param cls closure
    * @param merchant_payto_uri  merchant backend instance ID
    * @param instance_id the instance for which to check
    * @param exchange_url base URL of the exchange
    * @param[out] auth_ok true if @a access_token was set
    * @param[out] access_token set to access token for /kyc-info
    * @param[out] kyc_ok true if no urgent KYC work must be done for this account
    * @param[out] last_http_status set to last HTTP status from exchange on /kyc-check
    * @param[out] last_ec set to last Taler error code from exchange on /kyc-check
    * @param[out] rule_gen set to decision row at the exchange, 0 if no
    *    known decision of the exchange exists for this record; used
    *    for long-polling for changes to exchange decisions
    * @param[out] last_kyc_check set to time of last KYC check
    * @param[out] next_kyc_poll when should we check the KYC status next
    * @param[out] kyc_backoff current back-off frequency for KYC checks
    * @param[out] aml_review set to true if the account is under AML review (if this exposed)
    * @param[out] jlimits set to JSON array with AccountLimits, NULL if unknown (and likely defaults apply or KYC auth is urgently needed, see @a auth_ok)
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*get_kyc_status)(
     void *cls,
     struct TALER_FullPayto merchant_account_uri,
     const char *instance_id,
     const char *exchange_url,
     bool *auth_ok,
     struct TALER_AccountAccessTokenP *access_token,
     bool *kyc_ok,
     unsigned int *last_http_status,
     enum TALER_ErrorCode *last_ec,
     uint64_t *rule_gen,
     struct GNUNET_TIME_Timestamp *last_kyc_check,
     struct GNUNET_TIME_Absolute *next_kyc_poll,
     struct GNUNET_TIME_Relative *kyc_backoff,
     bool *aml_review,
     json_t **jlimits);
 
 
   /**
    * Check an account's KYC limits at an exchange.
    *
    * @param cls closure
    * @param merchant_payto_uri  merchant backend instance ID
    * @param instance_id the instance for which to check
    * @param exchange_url base URL of the exchange
    * @param[out] kyc_ok true if no urgent KYC work must be done for this account
    * @param[out] no_access_token true if we do not have a valid KYC access token (KYC auth missing)
    * @param[out] jlimits set to JSON array with AccountLimits, NULL if unknown (and likely defaults apply or KYC auth is urgently needed, see @a auth_ok)
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*get_kyc_limits)(
     void *cls,
     struct TALER_FullPayto merchant_account_uri,
     const char *instance_id,
     const char *exchange_url,
     bool *kyc_ok,
     bool *no_access_token,
     json_t **jlimits);
 
 
   /**
    * Update an instance's account's KYC status.
    *
    * @param cls closure
    * @param merchant_id merchant backend instance ID
    * @param h_wire hash of the wire account to check
    * @param exchange_url base URL of the exchange to check
    * @param timestamp timestamp to store
    * @param next_time when should we next check the KYC status
    * @param kyc_backoff what is the current backoff between KYC status checks
    * @param exchange_http_status HTTP status code returned last by the exchange
    * @param exchange_ec_code Taler error code returned last by the exchange
    * @param rule_gen generation of the rule in the exchange database
    *      (useful for long-polling to wait for rule changes)
    * @param access_token access token for the KYC process, NULL for none
    * @param jlimits JSON array with AccountLimits returned by the exchange
    * @param in_aml_review true if the exchange says the account is under review
    * @param kyc_ok current KYC status (true for satisfied)
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*account_kyc_set_status)(
     void *cls,
     const char *merchant_id,
     const struct TALER_MerchantWireHashP *h_wire,
     const char *exchange_url,
     struct GNUNET_TIME_Timestamp timestamp,
     struct GNUNET_TIME_Absolute next_time,
     struct GNUNET_TIME_Relative kyc_backoff,
     unsigned int exchange_http_status,
     enum TALER_ErrorCode exchange_ec_code,
     uint64_t rule_gen,
     const struct TALER_AccountAccessTokenP *access_token,
     const json_t *jlimits,
     bool in_aml_review,
     bool kyc_ok);
 
 
   /**
    * Set an instance's account's KYC status to failed.
    *
    * @param cls closure
    * @param merchant_id merchant backend instance ID
    * @param h_wire hash of the wire account to check
    * @param exchange_url base URL of the exchange to check
    * @param timestamp timestamp to store
    * @param exchange_http_status HTTP status code returned last by the exchange
    * @param kyc_ok current KYC status (should be false)
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*account_kyc_set_failed)(
     void *cls,
     const char *merchant_id,
     const struct TALER_MerchantWireHashP *h_wire,
     const char *exchange_url,
     struct GNUNET_TIME_Timestamp timestamp,
     unsigned int exchange_http_status,
     bool kyc_ok);
 
 
   /**
    * Lookup all of the products the given instance has configured.
    *
    * @param cls closure
    * @param instance_id instance to lookup products for
    * @param offset transfer_serial number of the transfer we want to offset from
    * @param limit number of entries to return, negative for descending,
    *                positive for ascending
    * @param category_filter filter products by category, NULL to not filter;
    *                uses the Postgresql "LIKE" pattern matcher, so
    *                "%" stands for any sequence of zero or more characters,
    *                "_" stands for any single character;
    *                use "\%" and "\_" to exactly match "%" or "_".
    *                We will always use case-insensitive searches, for case-sensitive
    *                matching the client should filter the result set.
    * @param name_filter filter products by name, NULL to not filter
    *                uses the Postgresql "LIKE" pattern matcher, so
    *                "%" stands for any sequence of zero or more characters,
    *                "_" stands for any single character
    *                use "\%" and "\_" to exactly match "%" or "_".
    *                We will always use case-insensitive searches, for case-sensitive
    *                matching the client should filter the result set.
    * @param description_filter filter products by description, NULL to not filter
    *                uses the Postgresql "LIKE" pattern matcher, so
    *                "%" stands for any sequence of zero or more characters,
    *                "_" stands for any single character
    *                use "\%" and "\_" to exactly match "%" or "_".
    *                We will always use case-insensitive searches, for case-sensitive
    *                matching the client should filter the result set.
    * @param product_group_id_filter only return products in where the
    *                product group ID matches the given ID, 0 to not filter
    * @param cb function to call on all products found
    * @param cb_cls closure for @a cb
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_products)(void *cls,
                        const char *instance_id,
                        uint64_t offset,
                        int64_t limit,
                        const char *category_filter,
                        const char *name_filter,
                        const char *description_filter,
                        uint64_t product_group_id_filter,
                        TALER_MERCHANTDB_ProductsCallback cb,
                        void *cb_cls);
 
 
   /**
    * Lookup full details of all of the products the given instance has configured (expensive).
    *
    * @param cls closure
    * @param instance_id instance to lookup products for
    * @param cb function to call on all products found
    * @param cb_cls closure for @a cb
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_all_products)(void *cls,
                            const char *instance_id,
                            TALER_MERCHANTDB_ProductCallback cb,
                            void *cb_cls);
 
   /**
    * Lookup inventory details for all products of an instance.
    *
    * @param cls closure
    * @param instance_id instance to lookup products for
    * @param cb function to call on all products found
    * @param cb_cls closure for @a cb
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_inventory_products)(void *cls,
                                  const char *instance_id,
                                  TALER_MERCHANTDB_InventoryProductCallback cb,
                                  void *cb_cls);
 
   /**
    * Lookup inventory details for a subset of products.
    *
    * @param cls closure
    * @param instance_id instance to lookup products for
    * @param product_ids product IDs to include (can be NULL/empty)
    * @param num_product_ids number of entries in @a product_ids
    * @param categories category IDs to include (can be NULL/empty)
    * @param num_categories number of entries in @a categories
    * @param cb function to call on all products found
    * @param cb_cls closure for @a cb
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_inventory_products_filtered)(
     void *cls,
     const char *instance_id,
     const char *const *product_ids,
     size_t num_product_ids,
     const uint64_t *categories,
     size_t num_categories,
     TALER_MERCHANTDB_InventoryProductCallback cb,
     void *cb_cls);
 
   /**
    * Call @a cb on each exchange we have in the database.
    *
    * @param cls closure
    * @param cb callback to invoke
    * @param cb_cls closure for @a cb
    * @return transaction status code
    */
   enum GNUNET_DB_QueryStatus
     (*select_exchanges) (void *cls,
                          TALER_MERCHANTDB_ExchangesCallback cb,
                          void *cb_cls);
 
   /**
    * Lookup details about a particular product.
    *
    * @param cls closure
    * @param instance_id instance to lookup products for
    * @param product_id product to lookup
    * @param[out] pd set to the product details on success, can be NULL
    *             (in that case we only want to check if the product exists)
    * @param[out] num_categories set to length of @a categories array
    * @param[out] categories set to array of categories the
    *   product is in, caller must free() it.
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_product)(void *cls,
                       const char *instance_id,
                       const char *product_id,
                       struct TALER_MERCHANTDB_ProductDetails *pd,
                       size_t *num_categories,
                       uint64_t **categories);
 
   /**
    * Lookup product image by its hash.
    *
    * @param cls closure
    * @param instance_id instance to lookup products for
    * @param image_hash lowercase hexadecimal representation of the SHA256 hash
    * @param[out] image set to base64-encoded data URL on success, caller must free()
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_product_image_by_hash)(void *cls,
                                     const char *instance_id,
                                     const char *image_hash,
                                     char **image);
 
   /**
    * Delete information about a product. Note that the transaction must
    * enforce that no stocks are currently locked.
    *
    * @param cls closure
    * @param instance_id instance to delete product of
    * @param product_id product to delete
    * @return DB status code, #GNUNET_DB_STATUS_SUCCESS_NO_RESULTS
    *           if locks prevent deletion OR product unknown
    */
   enum GNUNET_DB_QueryStatus
     (*delete_product)(void *cls,
                       const char *instance_id,
                       const char *product_id);
 
   /**
    * Insert details about a particular product.
    *
    * @param cls closure
    * @param instance_id instance to insert product for
    * @param product_id product identifier of product to insert
    * @param pd the product details to insert
    * @param num_cats length of @a cats array
    * @param cats array of categories the product is in
    * @param[out] no_instance set to true if @a instance_id is unknown
    * @param[out] conflict set to true if a conflicting
    *        product already exists in the database
    * @param[out] no_cat set to index of non-existing category from @a cats, or -1 if all @a cats were found
    * @param[out] no_group set to true if the product group in @a pd is unknown
    * @param[out] no_pot set to true if the money pot in @a pd is unknown
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*insert_product)(void *cls,
                       const char *instance_id,
                       const char *product_id,
                       const struct TALER_MERCHANTDB_ProductDetails *pd,
                       size_t num_cats,
                       const uint64_t *cats,
                       bool *no_instance,
                       bool *conflict,
                       ssize_t *no_cat,
                       bool *no_group,
                       bool *no_pot);
 
   /**
    * Update details about a particular product. Note that the
    * transaction must enforce that the sold/stocked/lost counters
    * are not reduced (i.e. by expanding the WHERE clause on the existing
    * values).
    *
    * @param cls closure
    * @param instance_id instance to lookup products for
    * @param product_id product to lookup
    * @param pd product details with updated values
    * @param num_cats length of @a cats array
    * @param cats number of categories the product is in
    * @param[out] no_instance the update failed as the instance is unknown
    * @param[out] no_cat set to -1 on success, otherwise the update failed and this is set
    *                to the index of a category in @a cats that is unknown
    * @param[out] no_product the @a product_id is unknown
    * @param[out] lost_reduced the update failed as the counter of units lost would have been lowered
    * @param[out] sold_reduced the update failed as the counter of units sold would have been lowered
    * @param[out] stocked_reduced the update failed as the counter of units stocked would have been lowered
    * @param[out] no_group set to true if the product group in @a pd is unknown
    * @param[out] no_pot set to true if the money pot in @a pd is unknown
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*update_product)(void *cls,
                       const char *instance_id,
                       const char *product_id,
                       const struct TALER_MERCHANTDB_ProductDetails *pd,
                       size_t num_cats,
                       const uint64_t *cats,
                       bool *no_instance,
                       ssize_t *no_cat,
                       bool *no_product,
                       bool *lost_reduced,
                       bool *sold_reduced,
                       bool *stocked_reduced,
                       bool *no_group,
                       bool *no_pot);
 
 
   /**
    * Lock stocks of a particular product. Note that the transaction must
    * enforce that the "stocked-sold-lost >= locked" constraint holds.
    *
    * @param cls closure
    * @param instance_id instance to lookup products for
    * @param product_id product to lookup
    * @param uuid the UUID that holds the lock
    * @param quantity how many units should be locked
    * @param quantity_frac fractional component of units to lock, in units of
    *        1/1000000 of the base value
    * @param expiration_time when should the lock expire
    * @return database result code, #GNUNET_DB_STATUS_SUCCESS_NO_RESULTS if the
    *         product is unknown OR if there insufficient stocks remaining
    */
   enum GNUNET_DB_QueryStatus
     (*lock_product)(void *cls,
                     const char *instance_id,
                     const char *product_id,
                     const struct GNUNET_Uuid *uuid,
                     uint64_t quantity,
                     uint32_t quantity_frac,
                     struct GNUNET_TIME_Timestamp expiration_time);
 
 
   /**
    * Release all expired product locks, including
    * those from expired offers -- across all
    * instances.
    *
    * @param cls closure
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*expire_locks)(void *cls);
 
 
   /**
    * Delete information about an order. Note that the transaction must
    * enforce that the order is not awaiting payment anymore.
    *
    * @param cls closure
    * @param instance_id instance to delete order of
    * @param order_id order to delete
    * @param force force deletion of claimed but unpaid orders
    * @return DB status code, #GNUNET_DB_STATUS_SUCCESS_NO_RESULTS
    *           if locks prevent deletion OR order unknown
    */
   enum GNUNET_DB_QueryStatus
     (*delete_order)(void *cls,
                     const char *instance_id,
                     const char *order_id,
                     bool force);
 
 
   /**
    * Retrieve order given its @a order_id and the @a instance_id.
    *
    * @param cls closure
    * @param instance_id instance to obtain order of
    * @param order_id order id used to perform the lookup
    * @param[out] claim_token the claim token generated for the order,
    *             NULL to only test if the order exists
    * @param[out] h_post_data set to the hash of the POST data that created the order
    * @param[out] contract_terms where to store the retrieved contract terms,
    *             NULL to only test if the order exists
    * @return transaction status
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_order)(void *cls,
                     const char *instance_id,
                     const char *order_id,
                     struct TALER_ClaimTokenP *claim_token,
                     struct TALER_MerchantPostDataHashP *h_post_data,
                     json_t **contract_terms);
 
 
   /**
    * Retrieve order summary given its @a order_id and the @a instance_id.
    *
    * @param cls closure
    * @param instance_id instance to obtain order of
    * @param order_id order id used to perform the lookup
    * @param[out] timestamp when was the order created
    * @param[out] order_serial under which serial do we keep this order
    * @return transaction status
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_order_summary)(void *cls,
                             const char *instance_id,
                             const char *order_id,
                             struct GNUNET_TIME_Timestamp *timestamp,
                             uint64_t *order_serial);
 
 
   /**
    * Retrieve orders given the @a instance_id.
    *
    * @param cls closure
    * @param instance_id instance to obtain order of
    * @param of filter to apply when looking up orders
    * @param[out] contract_terms where to store the retrieved contract terms,
    *             NULL to only test if the order exists
    * @return transaction status
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_orders)(void *cls,
                      const char *instance_id,
                      const struct TALER_MERCHANTDB_OrderFilter *of,
                      TALER_MERCHANTDB_OrdersCallback cb,
                      void *cb_cls);
 
 
   /**
    * Insert order into db.
    *
    * @param cls closure
    * @param instance_id identifies the instance responsible for the order
    * @param order_id alphanumeric string that uniquely identifies the order
    * @param session_id session ID for the order
    * @param h_post_data hash of the POST data for idempotency checks
    * @param pay_deadline how long does the customer have to pay for the order
    * @param claim_token token to use for access control
    * @param contract_terms proposal data to store
    * @param pos_key encoded key for payment verification
    * @param pos_algorithm algorithm to compute the payment verification
    * @return transaction status
    */
   enum GNUNET_DB_QueryStatus
     (*insert_order)(void *cls,
                     const char *instance_id,
                     const char *order_id,
                     const char *session_id,
                     const struct TALER_MerchantPostDataHashP *h_post_data,
                     struct GNUNET_TIME_Timestamp pay_deadline,
                     const struct TALER_ClaimTokenP *claim_token,
                     const json_t *contract_terms,
                     const char *pos_key,
                     enum TALER_MerchantConfirmationAlgorithm pos_algorithm);
 
 
   /**
    * Insert unclaim signature into DB and unclaim the order.
    *
    * @param cls closure
    * @param instance_id instance of the operation (checked)
    * @param merchant_pub public key of the instance (for notifications)
    * @param order_id identifies the order to unclaim
    * @param nonce claim nonce of the original claim
    * @param h_contract hash of the contract to unclaim
    * @param nsig signature by the nonce private key authorizing the unclaim
    * @return transaction status, 0 if an order with this @a nonce
    *   and @a h_contract was not found; 1 if the request is idempotent
    */
   enum GNUNET_DB_QueryStatus
     (*insert_unclaim_signature)(
     void *cls,
     const char *instance_id,
     const struct TALER_MerchantPublicKeyP *merchant_pub,
     const char *order_id,
     const struct GNUNET_CRYPTO_EddsaPublicKey *nonce,
     const struct GNUNET_HashCode *h_contract,
     const struct GNUNET_CRYPTO_EddsaSignature *nsig);
 
 
   /**
    * Insert blinded signatures for an order.
    *
    * @param cls closure
    * @param order_id order ID to insert blinded signatures for
    * @param i index of the blinded signature in the output array
    * @param hash hash of the token
    * @param blinded_sigs JSON array of blinded signatures
    */
   enum GNUNET_DB_QueryStatus
     (*insert_order_blinded_sigs)(
     void *cls,
     const char *order_id,
     uint32_t i,
     const struct GNUNET_HashCode *hash,
     const struct GNUNET_CRYPTO_BlindedSignature *blind_sig);
 
 
   /**
    * Release an inventory lock by UUID. Releases ALL stocks locked under
    * the given UUID.
    *
    * @param cls closure
    * @param uuid the UUID to release locks for
    * @return transaction status,
    *   #GNUNET_DB_STATUS_SUCCESS_NO_RESULTS means there are no locks under @a uuid
    *   #GNUNET_DB_STATUS_SUCCESS_ONE_RESULT indicates success
    */
   enum GNUNET_DB_QueryStatus
     (*unlock_inventory)(void *cls,
                         const struct GNUNET_Uuid *uuid);
 
 
   /**
    * Lock inventory stock to a particular order.
    *
    * @param cls closure
    * @param instance_id identifies the instance responsible for the order
    * @param order_id alphanumeric string that uniquely identifies the order
    * @param product_id uniquely identifies the product to be locked
    * @param quantity how many units should be locked to the @a order_id
    * @param quantity_frac fractional component of the quantity to be locked,
    *        in units of 1/1000000 of the base value
    * @return transaction status,
    *   #GNUNET_DB_STATUS_SUCCESS_NO_RESULTS means there are insufficient stocks
    *   #GNUNET_DB_STATUS_SUCCESS_ONE_RESULT indicates success
    */
   enum GNUNET_DB_QueryStatus
     (*insert_order_lock)(void *cls,
                          const char *instance_id,
                          const char *order_id,
                          const char *product_id,
                          uint64_t quantity,
                          uint32_t quantity_frac);
 
 
   /**
    * Select blinded signatures for an order.
    *
    * @param cls closure
    * @param order_id order ID to select blinded signatures for
    * @param cb callback to call for each blinded signature found
    * @param cb_cls closure for @a cb
    */
   enum GNUNET_DB_QueryStatus
     (*select_order_blinded_sigs)(
     void *cls,
     const char *order_id,
     TALER_MERCHANTDB_BlindedSigCallback cb,
     void *cb_cls);
 
 
   /**
    * Retrieve contract terms given its @a order_id
    *
    * @param cls closure
    * @param instance_id instance's identifier
    * @param order_id order_id used to lookup.
    * @param[out] contract_terms where to store the result, NULL to only check for existence
    * @param[out] order_serial set to the order's serial number
    * @param[out] paid set to true if the order is fully paid
    * @param[out] claim_token set to the claim token, NULL to only check for existence
    * @param[out] pos_key encoded key for payment verification
    * @param[out] pos_algorithm set to algorithm to compute the payment verification
    * @return transaction status
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_contract_terms2)(
     void *cls,
     const char *instance_id,
     const char *order_id,
     json_t **contract_terms,
     uint64_t *order_serial,
     bool *paid,
     struct TALER_ClaimTokenP *claim_token,
     char **pos_key,
     enum TALER_MerchantConfirmationAlgorithm *pricing_algorithm);
 
 
   /**
    * Retrieve contract terms given its @a order_id
    *
    * @param cls closure
    * @param instance_id instance's identifier
    * @param order_id order_id used to lookup
    * @param session_id session_id to compare, can be NULL
    * @param[out] contract_terms where to store the result, NULL to only check for existence
    * @param[out] order_serial set to the order's serial number
    * @param[out] paid set to true if the order is fully paid
    * @param[out] wired set to true if the exchange wired the funds
    * @param[out] session_matches set to true if @a session_id matches session stored for this contract
    * @param[out] claim_token set to the claim token, NULL to only check for existence
    * @param[out] choice_index set to the choice index, -1 if not set
    * @return transaction status
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_contract_terms3)(
     void *cls,
     const char *instance_id,
     const char *order_id,
     const char *session_id,
     json_t **contract_terms,
     uint64_t *order_serial,
     bool *paid,
     bool *wired,
     bool *session_matches,
     struct TALER_ClaimTokenP *claim_token,
     int16_t *choice_index);
 
 
   /**
    * Retrieve contract terms given its @a order_id
    *
    * @param cls closure
    * @param instance_id instance's identifier
    * @param order_id order_id used to lookup.
    * @param[out] contract_terms where to store the result, NULL to only check for existence
    * @param[out] order_serial set to the order's serial number
    * @param[out] claim_token set to the claim token, NULL to only check for existence
    * @return transaction status
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_contract_terms)(
     void *cls,
     const char *instance_id,
     const char *order_id,
     json_t **contract_terms,
     uint64_t *order_serial,
     struct TALER_ClaimTokenP *claim_token);
 
 
   /**
    * Store contract terms given its @a order_id. Note that some attributes are
    * expected to be calculated inside of the function, like the hash of the
    * contract terms (to be hashed), the creation_time and pay_deadline (to be
    * obtained from the merchant_orders table). The "session_id" should be
    * initially set to the empty string.  The "fulfillment_url" and "refund_deadline"
    * must be extracted from @a contract_terms.
    *
    * @param cls closure
    * @param instance_id instance's identifier
    * @param order_id order_id used to store
    * @param claim_token the token belonging to the order
    * @param[out] order_serial set to the serial of the order
    * @return transaction status, #GNUNET_DB_STATUS_HARD_ERROR if @a contract_terms
    *          is malformed
    */
   enum GNUNET_DB_QueryStatus
     (*insert_contract_terms)(
     void *cls,
     const char *instance_id,
     const char *order_id,
     json_t *contract_terms,
     uint64_t *order_serial);
 
 
   /**
    * Update the contract terms stored for @a order_id. Note that some attributes are
    * expected to be calculated inside of the function, like the hash of the
    * contract terms (to be hashed), the creation_time and pay_deadline (to be
    * obtained from the merchant_orders table). The "session_id" should be
    * initially set to the empty string.  The "fulfillment_url" and "refund_deadline"
    * must be extracted from @a contract_terms.
    *
    * @param cls closure
    * @param instance_id instance's identifier
    * @param order_id order_id used to store
    * @param contract_terms contract to store
    * @return transaction status, #GNUNET_DB_STATUS_HARD_ERROR if @a contract_terms
    *          is malformed
    */
   enum GNUNET_DB_QueryStatus
     (*update_contract_terms)(void *cls,
                              const char *instance_id,
                              const char *order_id,
                              json_t *contract_terms);
 
 
   /**
    * Delete information about a contract. Note that the transaction must
    * enforce that the contract is not awaiting payment anymore AND was not
    * paid, or is past the legal expiration.
    *
    * @param cls closure
    * @param instance_id instance to delete order of
    * @param order_id order to delete
    * @param legal_expiration how long do we need to keep (paid) contracts on
    *          file for legal reasons (i.e. taxation)
    * @return DB status code, #GNUNET_DB_STATUS_SUCCESS_NO_RESULTS
    *           if locks prevent deletion OR order unknown
    */
   enum GNUNET_DB_QueryStatus
     (*delete_contract_terms)(void *cls,
                              const char *instance_id,
                              const char *order_id,
                              struct GNUNET_TIME_Relative legal_expiration);
 
 
   /**
    * Lookup information about coins that were successfully deposited for a
    * given contract.
    *
    * @param cls closure
    * @param instance_id instance to lookup deposits for
    * @param h_contract_terms proposal data's hashcode
    * @param cb function to call with payment data
    * @param cb_cls closure for @a cb
    * @return transaction status
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_deposits)(void *cls,
                        const char *instance_id,
                        const struct TALER_PrivateContractHashP *h_contract_terms
                        ,
                        TALER_MERCHANTDB_DepositsCallback cb,
                        void *cb_cls);
 
 
   /**
    * Insert an exchange signing key into our database.
    *
    * @param cls closure
    * @param master_pub exchange master public key used for @a master_sig
    * @param exchange_pub exchange signing key to insert
    * @param start_date when does the signing key become valid
    * @param expire_date when does the signing key stop being used
    * @param end_date when does the signing key become void as proof
    * @param master_sig signature of @a master_pub over the @a exchange_pub and the dates
    */
   enum GNUNET_DB_QueryStatus
     (*insert_exchange_signkey)(
     void *cls,
     const struct TALER_MasterPublicKeyP *master_pub,
     const struct TALER_ExchangePublicKeyP *exchange_pub,
     struct GNUNET_TIME_Timestamp start_date,
     struct GNUNET_TIME_Timestamp expire_date,
     struct GNUNET_TIME_Timestamp end_date,
     const struct TALER_MasterSignatureP *master_sig);
 
 
   /**
    * Insert deposit confirmation from the exchange into the database.
    *
    * @param cls closure
    * @param instance_id instance to lookup deposits for
    * @param deposit_timestamp time when the exchange generated the deposit confirmation
    * @param h_contract_terms proposal data's hashcode
    * @param exchange_url URL of the exchange that issued @a coin_pub
    * @param wire_transfer_deadline when do we expect the wire transfer from the exchange
    * @param total_without_fees deposited total in the batch without fees
    * @param wire_fee wire fee the exchange charges
    * @param h_wire hash of the wire details of the target account of the merchant
    * @param exchange_sig signature from exchange that coin was accepted
    * @param exchange_pub signing key that was used for @a exchange_sig
    * @param[out] batch_deposit_serial_id set to the table row
    * @return transaction status
    */
   enum GNUNET_DB_QueryStatus
     (*insert_deposit_confirmation)(
     void *cls,
     const char *instance_id,
     struct GNUNET_TIME_Timestamp deposit_timestamp,
     const struct TALER_PrivateContractHashP *h_contract_terms,
     const char *exchange_url,
     struct GNUNET_TIME_Timestamp wire_transfer_deadline,
     const struct TALER_Amount *total_without_fees,
     const struct TALER_Amount *wire_fee,
     const struct TALER_MerchantWireHashP *h_wire,
     const struct TALER_ExchangeSignatureP *exchange_sig,
     const struct TALER_ExchangePublicKeyP *exchange_pub,
     uint64_t *batch_deposit_serial_id);
 
 
   /**
    * Insert information about coin deposited as part of
    * a batch into the database.
    *
    * @param cls closure
    * @param offset offset of the coin in the batch
    * @param deposit_confirmation_serial_id deposit confirmation for the batch the coin is part of
    * @param coin_pub public key of the coin
    * @param coin_sig deposit signature of the coin
    * @param amount_with_fee amount the exchange will deposit for this coin
    * @param deposit_fee fee the exchange will charge for this coin
    * @param refund_fee fee the exchange will charge for refunds of coin
    * @param check_time at what time should we check the deposit status
    *        with the exchange (for settlement)
    * @return transaction status
    */
   enum GNUNET_DB_QueryStatus
     (*insert_deposit)(
     void *cls,
     uint32_t offset,
     uint64_t deposit_confirmation_serial_id,
     const struct TALER_CoinSpendPublicKeyP *coin_pub,
     const struct TALER_CoinSpendSignatureP *coin_sig,
     const struct TALER_Amount *amount_with_fee,
     const struct TALER_Amount *deposit_fee,
     const struct TALER_Amount *refund_fee,
     struct GNUNET_TIME_Absolute check_time);
 
 
   /**
    * Obtain refunds associated with a contract.
    *
    * @param cls closure, typically a connection to the db
    * @param instance_id instance to lookup refunds for
    * @param h_contract_terms hash code of the contract
    * @param rc function to call for each coin on which there is a refund
    * @param rc_cls closure for @a rc
    * @return transaction status
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_refunds)(void *cls,
                       const char *instance_id,
                       const struct TALER_PrivateContractHashP *h_contract_terms,
                       TALER_MERCHANTDB_RefundCallback rc,
                       void *rc_cls);
 
 
   /**
    * Retrieve details about tokens that were used for an order.
    *
    * @param cls closure
    * @param order_serial identifies the order
    * @param cb function to call for each used token
    * @param cb_cls closure for @a cb
    * @return transaction status
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_spent_tokens_by_order)(void *cls,
                                     uint64_t order_serial,
                                     TALER_MERCHANTDB_UsedTokensCallback cb,
                                     void *cb_cls);
 
 
   /**
    * Mark contract as paid and store the current @a session_id
    * for which the contract was paid. Deletes the underlying order
    * and marks the locked stocks of the order as sold.
    *
    * @param cls closure
    * @param instance_id instance to mark contract as paid for
    * @param h_contract_terms hash of the contract that is now paid
    * @param session_id the session that paid the contract
    * @return transaction status
    */
   enum GNUNET_DB_QueryStatus
     (*mark_contract_paid)(
     void *cls,
     const char *instance_id,
     const struct TALER_PrivateContractHashP *h_contract_terms,
     const char *session_id,
     int16_t choice_index);
 
 
   /**
    * Update session associated with a contract and return
    * the fulfillment URL and the refund status.
    *
    * @param cls closure
    * @param instance_id instance to mark contract as paid for
    * @param h_contract_terms hash of the contract that is now paid
    * @param session_id the session that paid the contract
    * @param[out] fulfillment_url set to the fulfillment URL (possibly NULL)
    * @param[out] refunded set to true if the order was refunded
    * @return transaction status
    */
   enum GNUNET_DB_QueryStatus
     (*update_contract_session)(
     void *cls,
     const char *instance_id,
     const struct TALER_PrivateContractHashP *h_contract_terms,
     const char *session_id,
     char **fulfillment_url,
     bool *refunded);
 
 
   /**
    * Function called during aborts to refund a coin. Marks the
    * respective coin as refunded.
    *
    * @param cls closure
    * @param instance_id instance to refund payment for
    * @param h_contract_terms hash of the contract to refund coin for
    * @param refund_timestamp timestamp of when the coin was refunded
    * @param coin_pub public key of the coin to refund (fully)
    * @param reason text justifying the refund
    * @return transaction status
    *        #GNUNET_DB_STATUS_SUCCESS_NO_RESULTS if @a coin_pub is unknown to us;
    *        #GNUNET_DB_STATUS_SUCCESS_ONE_RESULT if the request is valid,
    *        regardless of whether it actually increased the refund
    */
   enum GNUNET_DB_QueryStatus
     (*refund_coin)(void *cls,
                    const char *instance_id,
                    const struct TALER_PrivateContractHashP *h_contract_terms,
                    struct GNUNET_TIME_Timestamp refund_timestamp,
                    const struct TALER_CoinSpendPublicKeyP *coin_pub,
                    const char *reason);
 
 
   /**
    * Retrieve contract terms given its @a order_id
    *
    * @param cls closure
    * @param instance_id instance's identifier
    * @param order_id order to lookup contract for
    * @param[out] h_contract_terms set to the hash of the contract.
    * @param[out] paid set to the payment status of the contract
    * @return transaction status
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_order_status)(void *cls,
                            const char *instance_id,
                            const char *order_id,
                            struct TALER_PrivateContractHashP *h_contract_terms,
                            bool *paid);
 
   /**
    * Retrieve contract terms given its @a order_serial
    *
    * @param cls closure
    * @param instance_id instance's identifier
    * @param order_serial serial ID of the order to look up
    * @param[out] order_id set to ID of the order
    * @param[out] h_contract_terms set to the hash of the contract.
    * @param[out] paid set to the payment status of the contract
    * @return transaction status
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_order_status_by_serial)(void *cls,
                                      const char *instance_id,
                                      uint64_t order_serial,
                                      char **order_id,
                                      struct TALER_PrivateContractHashP *
                                      h_contract_terms,
                                      bool *paid);
 
 
   /**
    * Retrieve details about coins that were deposited for an order.
    *
    * @param cls closure
    * @param order_serial identifies the order
    * @param cb function to call for each deposited coin
    * @param cb_cls closure for @a cb
    * @return transaction status
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_deposits_by_order)(void *cls,
                                 uint64_t order_serial,
                                 TALER_MERCHANTDB_DepositedCoinsCallback cb,
                                 void *cb_cls);
 
 
   /**
    * Retrieve wire transfer details for all deposits associated with
    * a given @a order_serial.
    *
    * @param cls closure
    * @param order_serial identifies the order
    * @param cb function called with the wire transfer details
    * @param cb_cls closure for @a cb
    * @return transaction status
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_transfer_details_by_order)(
     void *cls,
     uint64_t order_serial,
     TALER_MERCHANTDB_OrderTransferDetailsCallback cb,
     void *cb_cls);
 
 
   /**
    * Update transfer status.
    *
    * @param cls closure
    * @param exchange_url the exchange that made the transfer
    * @param wtid wire transfer subject
    * @param next_attempt when should we try again (if ever)
    * @param http_status last HTTP status code from the server, 0 for timeout
    * @param ec current error state of checking the transfer
    * @param detail last error detail from the server, possibly NULL
    * @param needs_retry true if we should retry the request
    * @return database transaction status
    */
   enum GNUNET_DB_QueryStatus
     (*update_transfer_status)(
     void *cls,
     const char *exchange_url,
     const struct TALER_WireTransferIdentifierRawP *wtid,
     struct GNUNET_TIME_Absolute next_attempt,
     unsigned int http_status,
     enum TALER_ErrorCode ec,
     const char *detail,
     bool needs_retry);
 
 
   /**
    * Finalize transfer status with success.
    *
    * @param cls closure
    * @param exchange_url the exchange that made the transfer
    * @param wtid wire transfer subject
    * @param h_details hash over all of the aggregated deposits
    * @param total_amount total amount exchange claimed to have transferred
    * @param wire_fee wire fee charged by the exchange
    * @param exchange_pub key used to make @e exchange_sig
    * @param exchange_sig signature of the exchange over reconciliation data
    * @return database transaction status
    */
   enum GNUNET_DB_QueryStatus
     (*finalize_transfer_status)(
     void *cls,
     const char *exchange_url,
     const struct TALER_WireTransferIdentifierRawP *wtid,
     const struct GNUNET_HashCode *h_details,
     const struct TALER_Amount *total_amount,
     const struct TALER_Amount *wire_fee,
     const struct TALER_ExchangePublicKeyP *exchange_pub,
     const struct TALER_ExchangeSignatureP *exchange_sig);
 
 
   /**
    * Retrieve wire transfer details of wire details
    * that taler-merchant-exchange still needs to
    * investigate.
    *
    * @param cls closure
    * @param limit maximum number of results to return
    * @param cb function called with the wire transfer data
    * @param cb_cls closure for @a cb
    * @return transaction status
    */
   enum GNUNET_DB_QueryStatus
     (*select_open_transfers)(
     void *cls,
     uint64_t limit,
     TALER_MERCHANTDB_OpenTransferCallback cb,
     void *cb_cls);
 
 
   /**
    * Insert wire transfer details for a deposit.
    *
    * @param cls closure
    * @param deposit_serial serial number of the deposit
    * @param h_wire hash of the merchant's account that should receive the deposit
    * @param exchange_url URL of the exchange that is making the deposit
    * @param dd deposit transfer data from the exchange to store
    * @return transaction status
    */
   enum GNUNET_DB_QueryStatus
     (*insert_deposit_to_transfer)(void *cls,
                                   uint64_t deposit_serial,
                                   const struct TALER_MerchantWireHashP *h_wire,
                                   const char *exchange_url,
                                   const struct TALER_EXCHANGE_DepositData *dd);
 
 
   /**
    * Set 'wired' status for an order to 'true'.
    *
    * @param cls closure
    * @param order_serial serial number of the order
    * @return transaction status
    */
   enum GNUNET_DB_QueryStatus
     (*mark_order_wired)(void *cls,
                         uint64_t order_serial);
 
 
   /**
    * Function called when some backoffice staff decides to award or
    * increase the refund on an existing contract.  This function
    * MUST be called from within a transaction scope setup by the
    * caller as it executes multiple SQL statements.
    *
    * @param cls closure
    * @param instance_id instance identifier
    * @param order_id the order to increase the refund for
    * @param refund maximum refund to return to the customer for this contract
    * @param olc function to call to obtain legal refund
    *    limits per exchange, NULL for no limits
    * @param olc_cls closure for @a olc
    * @param reason 0-terminated UTF-8 string giving the reason why the customer
    *               got a refund (free form, business-specific)
    * @return transaction status
    *        #GNUNET_DB_STATUS_SUCCESS_NO_RESULTS if @a refund is ABOVE the amount we
    *        were originally paid and thus the transaction failed;
    *        #GNUNET_DB_STATUS_SUCCESS_ONE_RESULT if the request is valid,
    *        regardless of whether it actually increased the refund beyond
    *        what was already refunded (idempotency!)
    */
   enum TALER_MERCHANTDB_RefundStatus
     (*increase_refund)(
     void *cls,
     const char *instance_id,
     const char *order_id,
     const struct TALER_Amount *refund,
     TALER_MERCHANTDB_OperationLimitCallback olc,
     void *olc_cls,
     const char *reason);
 
 
   /**
    * Obtain detailed refund data associated with a contract.
    *
    * @param cls closure, typically a connection to the db
    * @param instance_id instance to lookup refunds for
    * @param h_contract_terms hash code of the contract
    * @param rc function to call for each coin on which there is a refund
    * @param rc_cls closure for @a rc
    * @return transaction status
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_refunds_detailed)(
     void *cls,
     const char *instance_id,
     const struct TALER_PrivateContractHashP *h_contract_terms,
     TALER_MERCHANTDB_RefundDetailCallback rc,
     void *rc_cls);
 
   /**
    * Insert refund proof data from the exchange into the database.
    *
    * @param cls closure
    * @param refund_serial serial number of the refund
    * @param exchange_sig signature from exchange that coin was refunded
    * @param exchange_pub signing key that was used for @a exchange_sig
    * @return transaction status
    */
   enum GNUNET_DB_QueryStatus
     (*insert_refund_proof)(
     void *cls,
     uint64_t refund_serial,
     const struct TALER_ExchangeSignatureP *exchange_sig,
     const struct TALER_ExchangePublicKeyP *exchange_pub);
 
 
   /**
    * Insert used token into the database.
    *
    * @param cls closure
    * @param h_contract_terms hash of the contract the token was used for
    * @param h_issue_pub hash of the token issue public key
    * @param use_pub token use public key
    * @param use_sig token use signature
    * @param issue_sig token issue signature
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*insert_spent_token)(
     void *cls,
     const struct TALER_PrivateContractHashP *
     h_contract_terms,
     const struct TALER_TokenIssuePublicKeyHashP *h_issue_pub,
     const struct TALER_TokenUsePublicKeyP *use_pub,
     const struct TALER_TokenUseSignatureP *use_sig,
     const struct TALER_TokenIssueSignature *issue_sig);
 
 
   /**
    * Insert issued token into the database.
    *
    * @param cls closure
    * @param h_contract_terms hash of the contract the token was issued for
    * @param h_issue_pub hash of the token issue public key used to sign the issued token
    * @param blind_sig resulting blind token issue signature
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*insert_issued_token)(
     void *cls,
     const struct TALER_PrivateContractHashP *h_contract_terms,
     const struct TALER_TokenIssuePublicKeyHashP *h_issue_pub,
     const struct TALER_BlindedTokenIssueSignature *blind_sig);
 
 
   /**
    * Lookup refund proof data.
    *
    * @param cls closure
    * @param refund_serial serial number of the refund
    * @param[out] exchange_sig set to signature from exchange
    * @param[out] exchange_pub signing key that was used for @a exchange_sig
    * @return transaction status
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_refund_proof)(
     void *cls,
     uint64_t refund_serial,
     struct TALER_ExchangeSignatureP *exchange_sig,
     struct TALER_ExchangePublicKeyP *exchange_pub);
 
 
   /**
    * Retrieve the order ID that was used to pay for a resource within a session.
    *
    * @param cls closure
    * @param instance_id instance to lookup the order from
    * @param fulfillment_url URL that canonically identifies the resource
    *        being paid for
    * @param session_id session id
    * @param allow_refunded_for_repurchase true to include refunded orders in repurchase detection
    * @param[out] order_id location to store the order ID that was used when
    *             paying for the resource URL
    * @return transaction status
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_order_by_fulfillment)(
     void *cls,
     const char *instance_id,
     const char *fulfillment_url,
     const char *session_id,
     bool allow_refunded_for_repurchase,
     char **order_id);
 
   /**
    * Update information about progress made by taler-merchant-wirewatch.
    *
    * @param cls closure
    * @param instance which instance does the account belong to
    * @param payto_uri which account is this about
    * @param last_serial last serial imported from the bank
    * @return transaction status
    */
   enum GNUNET_DB_QueryStatus
     (*update_wirewatch_progress)(
     void *cls,
     const char *instance,
     struct TALER_FullPayto payto_uri,
     uint64_t last_serial);
 
 
   /**
    * Select information about accounts which taler-merchant-wirewatch should work on.
    *
    * @param cls closure
    * @param cb function to call with results
    * @param cb_cls closure for @a cb
    * @return transaction status
    */
   enum GNUNET_DB_QueryStatus
     (*select_wirewatch_accounts)(
     void *cls,
     TALER_MERCHANTDB_WirewatchWorkCallback cb,
     void *cb_cls);
 
 
   /**
    * Insert information about a wire transfer the merchant has received.
    * Idempotent, will do nothing if the same wire transfer is already known.
    * Updates the @a bank_serial_id if an equivalent transfer exists where
    * the @a bank_serial_id was set to 0 (unknown).
    *
    * @param cls closure
    * @param instance_id instance to lookup the order from
    * @param exchange_url which exchange made the transfer
    * @param wtid identifier of the wire transfer
    * @param credit_amount how much did we receive
    * @param payto_uri what is the merchant's bank account that received the transfer
    * @param bank_serial_id bank serial transfer ID, 0 for none (use NULL in DB!)
    * @param[out] no_instance instance unknown to backend
    * @param[out] no_account bank account with @a payto_uri unknown to backend
    * @param[out] conflict transfer with same @a wtid but different @a credit_amount exists
    * @return transaction status
    */
   enum GNUNET_DB_QueryStatus
     (*insert_transfer)(
     void *cls,
     const char *instance_id,
     const char *exchange_url,
     const struct TALER_WireTransferIdentifierRawP *wtid,
     const struct TALER_Amount *credit_amount,
     struct TALER_FullPayto payto_uri,
     uint64_t bank_serial_id,
     bool *no_instance,
     bool *no_account,
     bool *conflict);
 
 
   /**
    * Delete information about a transfer. Note that transfers
    * confirmed by the exchange cannot be deleted anymore.
    *
    * @param cls closure
    * @param instance_id instance to delete transfer of
    * @param transfer_serial_id transfer to delete
    * @return DB status code, #GNUNET_DB_STATUS_SUCCESS_NO_RESULTS
    *           if deletion is prohibited OR transfer is unknown
    */
   enum GNUNET_DB_QueryStatus
     (*delete_transfer)(void *cls,
                        const char *instance_id,
                        uint64_t transfer_serial_id);
 
 
   /**
    * Check if information about a transfer exists with the
    * backend.  Returns no data, only the query status.
    *
    * @param cls closure
    * @param instance_id instance to delete transfer of
    * @param transfer_serial_id transfer to delete
    * @return DB status code, #GNUNET_DB_STATUS_SUCCESS_ONE_RESULT
    *           if the transfer record exists
    */
   enum GNUNET_DB_QueryStatus
     (*check_transfer_exists)(void *cls,
                              const char *instance_id,
                              uint64_t transfer_serial_id);
 
 
   /**
    * Lookup account serial by payto URI.
    *
    * @param cls closure
    * @param instance_id instance to lookup the account from
    * @param payto_uri what is the merchant's bank account to lookup
    * @param[out] account_serial serial number of the account
    * @return transaction status
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_account)(void *cls,
                       const char *instance_id,
                       struct TALER_FullPayto payto_uri,
                       uint64_t *account_serial);
 
 
   /**
    * Insert information about a wire transfer the merchant has received.
    *
    * @param cls closure
    * @param instance_id instance to provide transfer details for
    * @param exchange_url which exchange made the transfer
    * @param payto_uri what is the merchant's bank account that received the transfer
    * @param wtid identifier of the wire transfer
    * @param td transfer details to store
    * @return transaction status,
    *   #GNUNET_DB_STATUS_SUCCESS_NO_RESULTS if the @a wtid and @a exchange_uri are not known for this @a instance_id
    *   #GNUNET_DB_STATUS_SUCCESS_ONE_RESULT on success
    */
   enum GNUNET_DB_QueryStatus
     (*insert_transfer_details)(
     void *cls,
     const char *instance_id,
     const char *exchange_url,
     struct TALER_FullPayto payto_uri,
     const struct TALER_WireTransferIdentifierRawP *wtid,
     const struct TALER_EXCHANGE_TransferData *td);
 
 
   /**
    * Obtain information about wire fees charged by an exchange,
    * including signature (so we have proof).
    *
    * @param cls closure
    * @param master_pub master public key of the exchange
    * @param h_wire_method hash of wire method
    * @param contract_date date of the contract to use for the lookup
    * @param[out] fees set to wire fees charged
    * @param[out] start_date start of fee being used
    * @param[out] end_date end of fee being used
    * @param[out] master_sig signature of exchange over fee structure
    * @return transaction status code
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_wire_fee)(
     void *cls,
     const struct TALER_MasterPublicKeyP *master_pub,
     const char *wire_method,
     struct GNUNET_TIME_Timestamp contract_date,
     struct TALER_WireFeeSet *fees,
     struct GNUNET_TIME_Timestamp *start_date,
     struct GNUNET_TIME_Timestamp *end_date,
     struct TALER_MasterSignatureP *master_sig);
 
 
   /**
    * Obtain information about an expected incoming wire transfer.
    *
    * @param cls closure
    * @param instance_id instance to lookup payments for
    * @param expected_incoming_serial serial number of the transfer
    * @param[out] expected_time expected date of the transfer
    * @param[out] wtid expected wire transfer subject
    * @param[out] payto_uri target bank account
    * @param[out] exchange_url URL of the exchange
    * @param[out] execution_time, set to 0 if unknown
    * @param[out] confirmed set if the transfer was confirmed
    * @param[out] master_pub master public key of the exchange
    * @return transaction status code
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_expected_transfer)(
     void *cls,
     const char *instance_id,
     uint64_t expected_incoming_serial,
     struct GNUNET_TIME_Timestamp *expected_time,
     struct TALER_Amount *expected_credit_amount,
     struct TALER_WireTransferIdentifierRawP *wtid,
     struct TALER_FullPayto *payto_uri,
     char **exchange_url,
     struct GNUNET_TIME_Timestamp *execution_time,
     bool *confirmed,
     struct TALER_MasterPublicKeyP *master_pub);
 
 
   /**
    * Obtain reconciliation details for an expected incoming wire transfer.
    *
    * @param cls closure
    * @param instance_id instance to lookup payments for
    * @param expected_incoming_serial serial number of the transfer
    * @param cb callback to invoke
    * @param cb_cls closure for @a cb
    * @return transaction status code
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_reconciliation_details)(
     void *cls,
     const char *instance_id,
     uint64_t expected_incoming_serial,
     TALER_MERCHANTDB_ReconciliationDetailsCallback cb,
     void *cb_cls);
 
 
   /**
    * Lookup information about coin payments by @a h_contract_terms and
    * @a coin_pub.
    *
    * @param cls closure
    * @param instance_id instance to lookup payments for
    * @param h_contract_terms proposal data's hashcode
    * @param coin_pub public key to use for the search
    * @param cb function to call with payment data
    * @param cb_cls closure for @a cb
    * @return transaction status
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_deposits_by_contract_and_coin)(
     void *cls,
     const char *instance_id,
     const struct TALER_PrivateContractHashP *h_contract_terms,
     const struct TALER_CoinSpendPublicKeyP *coin_pub,
     TALER_MERCHANTDB_CoinDepositCallback cb,
     void *cb_cls);
 
 
   /**
    * Lookup transfer summary (used if we already verified the details).
    *
    * @param cls closure
    * @param exchange_url the exchange that made the transfer
    * @param wtid wire transfer subject
    * @param cb function to call with detailed transfer data
    * @param cb_cls closure for @a cb
    * @return transaction status
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_transfer_summary)(
     void *cls,
     const char *exchange_url,
     const struct TALER_WireTransferIdentifierRawP *wtid,
     TALER_MERCHANTDB_TransferSummaryCallback cb,
     void *cb_cls);
 
 
   /**
    * Lookup transfer details. Used if we still need to verify the details.
    *
    * @param cls closure
    * @param exchange_url the exchange that made the transfer
    * @param wtid wire transfer subject
    * @param cb function to call with detailed transfer data
    * @param cb_cls closure for @a cb
    * @return transaction status
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_transfer_details)(
     void *cls,
     const char *exchange_url,
     const struct TALER_WireTransferIdentifierRawP *wtid,
     TALER_MERCHANTDB_TransferDetailsCallback cb,
     void *cb_cls);
 
 
   /**
    * Lookup transfers.
    *
    * @param cls closure
    * @param instance_id instance to lookup payments for
    * @param payto_uri account that we are interested in transfers to
    * @param before timestamp for the earliest transfer we care about
    * @param after timestamp for the last transfer we care about
    * @param limit number of entries to return, negative for descending in execution time,
    *                positive for ascending in execution time
    * @param offset transfer_serial number of the transfer we want to offset from
    * @param expected filter for transfers that were expected
    * @param cb function to call with detailed transfer data
    * @param cb_cls closure for @a cb
    * @return transaction status
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_transfers)(
     void *cls,
     const char *instance_id,
     struct TALER_FullPayto payto_uri,
     struct GNUNET_TIME_Timestamp before,
     struct GNUNET_TIME_Timestamp after,
     int64_t limit,
     uint64_t offset,
     enum TALER_EXCHANGE_YesNoAll expected,
     TALER_MERCHANTDB_TransferCallback cb,
     void *cb_cls);
 
 
   /**
    * Lookup expected incoming transfers.
    *
    * @param cls closure
    * @param instance_id instance to lookup payments for
    * @param payto_uri account that we are interested in transfers to
    * @param before timestamp for the earliest transfer we care about
    * @param after timestamp for the last transfer we care about
    * @param limit number of entries to return, negative for descending in execution time,
    *                positive for ascending in execution time
    * @param offset expected_transfer_serial number of the transfer we want to offset from
    * @param confirmed filter by confirmation status
    * @param verified filter by verification status
    * @param cb function to call with detailed transfer data
    * @param cb_cls closure for @a cb
    * @return transaction status
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_expected_transfers)(
     void *cls,
     const char *instance_id,
     struct TALER_FullPayto payto_uri,
     struct GNUNET_TIME_Timestamp before,
     struct GNUNET_TIME_Timestamp after,
     int64_t limit,
     uint64_t offset,
     enum TALER_EXCHANGE_YesNoAll confirmed,
     enum TALER_EXCHANGE_YesNoAll verified,
     TALER_MERCHANTDB_IncomingCallback cb,
     void *cb_cls);
 
 
   /**
    * Store information about wire fees charged by an exchange,
    * including signature (so we have proof).
    *
    * @param cls closure
    * @param master_pub master public key of the exchange
    * @param h_wire_method hash of wire method
    * @param fees wire fees charged
    * @param start_date start of fee being used
    * @param end_date end of fee being used
    * @param master_sig signature of exchange over fee structure
    * @return transaction status code
    */
   enum GNUNET_DB_QueryStatus
     (*store_wire_fee_by_exchange)(
     void *cls,
     const struct TALER_MasterPublicKeyP *master_pub,
     const struct GNUNET_HashCode *h_wire_method,
     const struct TALER_WireFeeSet *fees,
     struct GNUNET_TIME_Timestamp start_date,
     struct GNUNET_TIME_Timestamp end_date,
     const struct TALER_MasterSignatureP *master_sig);
 
 
   /**
    * Delete information about wire accounts of an exchange. (Used when we got new account data.)
    *
    * @param cls closure
    * @param master_pub public key of the exchange
    * @return transaction status code
    */
   enum GNUNET_DB_QueryStatus
     (*delete_exchange_accounts)(
     void *cls,
     const struct TALER_MasterPublicKeyP *master_pub);
 
 
   /**
    * Return information about wire accounts of an exchange.
    *
    * @param cls closure
    * @param master_pub public key of the exchange
    * @param cb function to call on each account
    * @param cb_cls closure for @a cb
    * @return transaction status code
    */
   enum GNUNET_DB_QueryStatus
     (*select_accounts_by_exchange)(
     void *cls,
     const struct TALER_MasterPublicKeyP *master_pub,
     TALER_MERCHANTDB_ExchangeAccountCallback cb,
     void *cb_cls);
 
 
   /**
    * Insert information about a wire account of an exchange.
    *
    * @param cls closure
    * @param master_pub public key of the exchange
    * @param payto_uri URI of the bank account
    * @param conversion_url conversion service, NULL if there is no conversion required
    * @param debit_restrictions JSON array of debit restrictions on the account
    * @param credit_restrictions JSON array of debit restrictions on the account
    * @param master_sig signature affirming the account of the exchange
    * @return transaction status code
    */
   enum GNUNET_DB_QueryStatus
     (*insert_exchange_account)(
     void *cls,
     const struct TALER_MasterPublicKeyP *master_pub,
     const struct TALER_FullPayto payto_uri,
     const char *conversion_url,
     const json_t *debit_restrictions,
     const json_t *credit_restrictions,
     const struct TALER_MasterSignatureP *master_sig);
 
 
   /**
    * Lookup all of the templates the given instance has configured.
    *
    * @param cls closure
    * @param instance_id instance to lookup template for
    * @param cb function to call on all template found
    * @param cb_cls closure for @a cb
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_templates)(void *cls,
                         const char *instance_id,
                         TALER_MERCHANTDB_TemplatesCallback cb,
                         void *cb_cls);
 
 
   /**
    * Lookup details about a particular template.
    *
    * @param cls closure
    * @param instance_id instance to lookup template for
    * @param template_id template to lookup
    * @param[out] td set to the template details on success, can be NULL
    *             (in that case we only want to check if the template exists)
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_template)(void *cls,
                        const char *instance_id,
                        const char *template_id,
                        struct TALER_MERCHANTDB_TemplateDetails *td);
 
   /**
    * Delete information about a template.
    *
    * @param cls closure
    * @param instance_id instance to delete template of
    * @param template_id template to delete
    * @return DB status code, #GNUNET_DB_STATUS_SUCCESS_NO_RESULTS
    *           if template unknown.
    */
   enum GNUNET_DB_QueryStatus
     (*delete_template)(void *cls,
                        const char *instance_id,
                        const char *template_id);
 
 
   /**
    * Insert details about a particular template.
    *
    * @param cls closure
    * @param instance_id instance to insert template for
    * @param template_id template identifier of template to insert
    * @param otp_serial_id 0 if no OTP device is associated
    * @param td the template details to insert
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*insert_template)(void *cls,
                        const char *instance_id,
                        const char *template_id,
                        uint64_t otp_serial_id,
                        const struct TALER_MERCHANTDB_TemplateDetails *td);
 
 
   /**
    * Update details about a particular template.
    *
    * @param cls closure
    * @param instance_id instance to update template for
    * @param template_id template to update
    * @param td update to the template details on success, can be NULL
    *             (in that case we only want to check if the template exists)
    * @return database result code, #GNUNET_DB_STATUS_SUCCESS_NO_RESULTS if the template
    *         does not yet exist.
    */
   enum GNUNET_DB_QueryStatus
     (*update_template)(void *cls,
                        const char *instance_id,
                        const char *template_id,
                        const struct TALER_MERCHANTDB_TemplateDetails *td);
 
 
   /**
    * Delete information about an OTP device.
    *
    * @param cls closure
    * @param instance_id instance to delete OTP device of
    * @param otp_id otp device to delete
    * @return DB status code, #GNUNET_DB_STATUS_SUCCESS_NO_RESULTS
    *           if template unknown.
    */
   enum GNUNET_DB_QueryStatus
     (*delete_otp)(void *cls,
                   const char *instance_id,
                   const char *otp_id);
 
   /**
    * Insert details about a particular OTP device.
    *
    * @param cls closure
    * @param instance_id instance to insert OTP device for
    * @param otp_id otp identifier of OTP device to insert
    * @param td the OTP device details to insert
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*insert_otp)(void *cls,
                   const char *instance_id,
                   const char *otp_id,
                   const struct TALER_MERCHANTDB_OtpDeviceDetails *td);
 
 
   /**
    * Update details about a particular OTP device.
    *
    * @param cls closure
    * @param instance_id instance to update OTP device for
    * @param otp_id OTP device to update
    * @param td update to the OTP device details on success, can be NULL
    *             (in that case we only want to check if the template exists)
    * @return database result code, #GNUNET_DB_STATUS_SUCCESS_NO_RESULTS if the template
    *         does not yet exist.
    */
   enum GNUNET_DB_QueryStatus
     (*update_otp)(void *cls,
                   const char *instance_id,
                   const char *otp_id,
                   const struct TALER_MERCHANTDB_OtpDeviceDetails *td);
 
   /**
    * Lookup all of the OTP devices the given instance has configured.
    *
    * @param cls closure
    * @param instance_id instance to lookup OTP devices for
    * @param cb function to call on all OTP devices found
    * @param cb_cls closure for @a cb
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_otp_devices)(void *cls,
                           const char *instance_id,
                           TALER_MERCHANTDB_OtpDeviceCallback cb,
                           void *cb_cls);
 
 
   /**
    * Lookup details about an OTP device.
    *
    * @param cls closure
    * @param instance_id instance to lookup template for
    * @param otp_id OTP device to lookup
    * @param[out] td set to the OTP device details on success, can be NULL
    *             (in that case we only want to check if the template exists)
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*select_otp)(void *cls,
                   const char *instance_id,
                   const char *otp_id,
                   struct TALER_MERCHANTDB_OtpDeviceDetails *td);
 
 
   /**
    * Lookup serial number of an OTP device.
    *
    * @param cls closure
    * @param instance_id instance to lookup template for
    * @param otp_id OTP device to lookup
    * @param[out] serial set to the OTP device serial number   * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*select_otp_serial)(void *cls,
                          const char *instance_id,
                          const char *otp_id,
                          uint64_t *serial);
 
   /**
    * Delete information about a measurement unit.
    *
    * @param cls closure
    * @param instance_id instance to delete unit from
    * @param unit_id symbolic identifier of the unit
    * @param[out] no_instance set to true if @a instance_id is unknown
    * @param[out] no_unit set to true if the unit does not exist
    * @param[out] builtin_conflict set to true if the unit is builtin and may not be deleted
    * @return DB status code
    */
   enum GNUNET_DB_QueryStatus
     (*delete_unit)(void *cls,
                    const char *instance_id,
                    const char *unit_id,
                    bool *no_instance,
                    bool *no_unit,
                    bool *builtin_conflict);
 
   /**
    * Insert a measurement unit definition.
    *
    * @param cls closure
    * @param instance_id instance to insert unit for
    * @param ud unit details to store (unit_serial ignored)
    * @param[out] no_instance set to true if @a instance_id is unknown
    * @param[out] conflict set to true if a conflicting unit already exists
    * @param[out] unit_serial set to the inserted serial on success
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*insert_unit)(void *cls,
                    const char *instance_id,
                    const struct TALER_MERCHANTDB_UnitDetails *ud,
                    bool *no_instance,
                    bool *conflict,
                    uint64_t *unit_serial);
 
   /**
    * Update a measurement unit definition.
    *
    * @param cls closure
    * @param instance_id instance owning the unit
    * @param unit_id symbolic identifier of the unit
    * @param unit_name_long optional new long label (NULL to keep current)
    * @param unit_name_long_i18n optional new long-label translations (NULL to keep current)
    * @param unit_name_short optional new short label (NULL to keep current)
    * @param unit_name_short_i18n optional new short-label translations (NULL to keep current)
    * @param unit_allow_fraction optional new fractional toggle (NULL to keep current)
    * @param unit_precision_level optional new fractional precision (NULL to keep current)
    * @param unit_active optional new visibility flag (NULL to keep current)
    * @param[out] no_instance set if instance unknown
    * @param[out] no_unit set if unit unknown
    * @param[out] builtin_conflict set if immutable builtin fields touched
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*update_unit)(void *cls,
                    const char *instance_id,
                    const char *unit_id,
                    const char *unit_name_long,
                    const json_t *unit_name_long_i18n,
                    const char *unit_name_short,
                    const json_t *unit_name_short_i18n,
                    const bool *unit_allow_fraction,
                    const uint32_t *unit_precision_level,
                    const bool *unit_active,
                    bool *no_instance,
                    bool *no_unit,
                    bool *builtin_conflict);
 
   /**
    * Lookup all measurement units of an instance.
    *
    * @param cls closure
    * @param instance_id instance to fetch units for
    * @param cb function to call per unit
    * @param cb_cls closure for @a cb
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_units)(void *cls,
                     const char *instance_id,
                     TALER_MERCHANTDB_UnitsCallback cb,
                     void *cb_cls);
 
   /**
    * Lookup custom measurement units by name.
    *
    * @param cls closure
    * @param instance_id instance to fetch units for
    * @param units array of unit identifiers
    * @param num_units length of @a units
    * @param cb function to call per unit
    * @param cb_cls closure for @a cb
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_custom_units_by_names)(void *cls,
                                     const char *instance_id,
                                     const char *const *units,
                                     size_t num_units,
                                     TALER_MERCHANTDB_UnitsCallback cb,
                                     void *cb_cls);
   /**
    * Lookup a single measurement unit.
    *
    * @param cls closure
    * @param instance_id instance to fetch unit for
    * @param unit_id symbolic identifier
    * @param[out] ud unit details on success; may be NULL to test existence
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*select_unit)(void *cls,
                    const char *instance_id,
                    const char *unit_id,
                    struct TALER_MERCHANTDB_UnitDetails *ud);
 
 
   /**
    * Delete information about a product category.
    *
    * @param cls closure
    * @param instance_id instance to delete category of
    * @param category_id identifies the category to delete
    * @return DB status code, #GNUNET_DB_STATUS_SUCCESS_NO_RESULTS
    *           if template unknown.
    */
   enum GNUNET_DB_QueryStatus
     (*delete_category)(void *cls,
                        const char *instance_id,
                        uint64_t category_id);
 
   /**
    * Insert new product category.
    *
    * @param cls closure
    * @param instance_id instance to insert OTP device for
    * @param category_name name of the category
    * @param category_name_i18n translations of the category name
    * @param[out] category_id set to the category id on success
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*insert_category)(void *cls,
                        const char *instance_id,
                        const char *category_name,
                        const json_t *category_name_i18n,
                        uint64_t *category_id);
 
 
   /**
    * Update descriptions of a product category.
    *
    * @param cls closure
    * @param instance_id instance to update OTP device for
    * @param category_id category to update
    * @param category_name name of the category
    * @param category_name_i18n translations of the category name
    * @return database result code, #GNUNET_DB_STATUS_SUCCESS_NO_RESULTS if the template
    *         does not yet exist.
    */
   enum GNUNET_DB_QueryStatus
     (*update_category)(void *cls,
                        const char *instance_id,
                        uint64_t category_id,
                        const char *category_name,
                        const json_t *category_name_i18n);
 
   /**
    * Lookup all of the product categories the given instance has configured.
    *
    * @param cls closure
    * @param instance_id instance to lookup OTP devices for
    * @param cb function to call on all categories found
    * @param cb_cls closure for @a cb
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_categories)(void *cls,
                          const char *instance_id,
                          TALER_MERCHANTDB_CategoriesCallback cb,
                          void *cb_cls);
 
   /**
    * Lookup product categories by ID.
    *
    * @param cls closure
    * @param instance_id instance to lookup categories for
    * @param category_ids array of category IDs
    * @param num_category_ids length of @a category_ids
    * @param cb function to call on all categories found
    * @param cb_cls closure for @a cb
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_categories_by_ids)(void *cls,
                                 const char *instance_id,
                                 const uint64_t *category_ids,
                                 size_t num_category_ids,
                                 TALER_MERCHANTDB_CategoriesCallback cb,
                                 void *cb_cls);
 
 
   /**
    * Lookup details about product category.
    *
    * @param cls closure
    * @param instance_id instance to lookup template for
    * @param category_id category to update
    * @param[out] cd set to the category details on success, can be NULL
    *             (in that case we only want to check if the category exists)
    * @param[out] num_products set to length of @a products array
    * @param[out] products set to buffer with @a num_products 0-terminated strings with the product IDs, caller must free() it.
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*select_category)(void *cls,
                        const char *instance_id,
                        uint64_t category_id,
                        struct TALER_MERCHANTDB_CategoryDetails *cd,
                        size_t *num_products,
                        char **products);
 
 
   /**
    * Lookup details about product category by name.
    *
    * @param cls closure
    * @param instance_id instance to lookup template for
    * @param category_name category name to look for
    * @param[out] name_i18n category name translation
    * @param[out] category_id category ID
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*select_category_by_name)(void *cls,
                                const char *instance_id,
                                const char *category_name,
                                json_t **name_i18n,
                                uint64_t *category_id);
 
 
   /**
    * Lookup all of the webhooks the given instance has configured.
    *
    * @param cls closure
    * @param instance_id instance to lookup webhook for
    * @param cb function to call on all webhook found
    * @param cb_cls closure for @a cb
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_webhooks)(void *cls,
                        const char *instance_id,
                        TALER_MERCHANTDB_WebhooksCallback cb,
                        void *cb_cls);
 
 
   /**
    * Lookup details about a particular webhook.
    *
    * @param cls closure
    * @param instance_id instance to lookup webhook for
    * @param webhook_id webhook to lookup
    * @param[out] wb set to the webhook details on success, can be NULL
    *             (in that case we only want to check if the webhook exists)
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_webhook)(void *cls,
                       const char *instance_id,
                       const char *webhook_id,
                       struct TALER_MERCHANTDB_WebhookDetails *wb);
 
   /**
    * Delete information about a webhook.
    *
    * @param cls closure
    * @param instance_id instance to delete webhook of
    * @param webhook_id webhook to delete
    * @return DB status code, #GNUNET_DB_STATUS_SUCCESS_NO_RESULTS
    *           if webhook unknown.
    */
   enum GNUNET_DB_QueryStatus
     (*delete_webhook)(void *cls,
                       const char *instance_id,
                       const char *webhook_id);
 
 
   /**
    * Insert details about a particular webhook.
    *
    * @param cls closure
    * @param instance_id instance to insert webhook for
    * @param webhook_id webhook identifier of webhook to insert
    * @param wb the webhook details to insert
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*insert_webhook)(void *cls,
                       const char *instance_id,
                       const char *webhook_id,
                       const struct TALER_MERCHANTDB_WebhookDetails *wb);
 
 
   /**
    * Update details about a particular webhook.
    *
    * @param cls closure
    * @param instance_id instance to update webhook for
    * @param webhook_id webhook to update
    * @param wb update to the webhook details on success, can be NULL
    *             (in that case we only want to check if the webhook exists)
    * @return database result code, #GNUNET_DB_STATUS_SUCCESS_NO_RESULTS if the webhook
    *         does not yet exist.
    */
   enum GNUNET_DB_QueryStatus
     (*update_webhook)(void *cls,
                       const char *instance_id,
                       const char *webhook_id,
                       const struct TALER_MERCHANTDB_WebhookDetails *wb);
 
   /**
    * Lookup webhook by event
    *
    * @param cls closure
    * @param instance_id instance to lookup webhook for
    * @param event_type event that we need to put in the pending webhook
    * @param[out] cb set to the webhook details on success
    * @param cb_cls callback closure
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_webhook_by_event)(void *cls,
                                const char *instance_id,
                                const char *event_type,
                                TALER_MERCHANTDB_WebhookDetailCallback cb,
                                void *cb_cls);
 
   /**
    * Insert webhook in the pending webhook.
    *
    * @param cls closure
    * @param instance_id instance to insert webhook for
    * @param webhook_serial webhook to insert in the pending webhook
    * @param url to make the request to
    * @param http_method for the webhook
    * @param header of the webhook
    * @param body of the webhook
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*insert_pending_webhook)(void *cls,
                               const char *instance_id,
                               uint64_t webhook_serial,
                               const char *url,
                               const char *http_method,
                               const char *header,
                               const char *body);
   /**
    * Lookup the webhook that need to be send in priority. These webhooks are not successfully
    * send.
    *
    * @param cls closure
    * @param cb pending webhook callback
    * @param cb_cls callback closure
    */
   // WHERE next_attempt <= now ORDER BY next_attempt ASC
   enum GNUNET_DB_QueryStatus
     (*lookup_pending_webhooks)(void *cls,
                                TALER_MERCHANTDB_PendingWebhooksCallback cb,
                                void *cb_cls);
 
   /**
    * Lookup future webhook in the pending webhook that need to be send.
    * With that we can know how long the system can 'sleep'.
    *
    * @param cls closure
    * @param cb pending webhook callback
    * @param cb_cls callback closure
    */
   // ORDER BY next_attempt ASC LIMIT 1
   enum GNUNET_DB_QueryStatus
     (*lookup_future_webhook)(void *cls,
                              TALER_MERCHANTDB_PendingWebhooksCallback cb,
                              void *cb_cls);
 
   /**
    * Lookup all the webhooks in the pending webhook.
    * Use by the administrator
    *
    * @param cls closure
    * @param instance_id to lookup webhooks for this instance particularly
    * @param min_row to see the list of the pending webhook that it is started with this minimum row.
    * @param max_results to see the list of the pending webhook that it is end with this max results.
    * @param cb pending webhook callback
    * @param cb_cls callback closure
    */
   // WHERE webhook_pending_serial > min_row ORDER BY webhook_pending_serial ASC LIMIT max_results
   enum GNUNET_DB_QueryStatus
     (*lookup_all_webhooks)(void *cls,
                            const char *instance_id,
                            uint64_t min_row,
                            uint32_t max_results,
                            TALER_MERCHANTDB_PendingWebhooksCallback cb,
                            void *cb_cls);
 
 
   /**
    * Update the pending webhook. It is use if the webhook can't be send.
    *
    * @param cls closure
    * @param webhook_serial webhook that need to be update
    * @param next_attempt when we should make the next request to the webhook
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*update_pending_webhook)(void *cls,
                               uint64_t webhook_pending_serial,
                               struct GNUNET_TIME_Absolute next_attempt);
   // maybe add: http status of failure?
 
 
   /**
    * Delete a webhook in the pending webhook after the
    * webhook was completed successfully.
    *
    * @param cls closure
    * @param webhook_serial webhook that need to be delete in the pending webhook
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*delete_pending_webhook)(void *cls,
                               uint64_t webhook_pending_serial);
 
 
   /**
    * Retrieve exchange's keys from the database.
    *
    * @param cls plugin closure
    * @param exchange_url base URL of the exchange
    * @param[out] first_retry set to earliest we may retry fetching the keys
    * @param[out] keys set to the keys of the exchange
    * @return transaction status
    */
   enum GNUNET_DB_QueryStatus
     (*select_exchange_keys)(void *cls,
                             const char *exchange_url,
                             struct GNUNET_TIME_Absolute *first_retry,
                             struct TALER_EXCHANGE_Keys **keys);
 
 
   /**
    * Insert or update @a keys into the database.
    *
    * @param cls plugin closure
    * @param exchange_url base URL of the exchange
    * @param keys data to store
    * @param first_retry earliest we may retry fetching the keys
    * @param http_status latest HTTP status of the exchange
    * @param ec latest error code from fetching /keys
    * @return transaction status
    */
   enum GNUNET_DB_QueryStatus
     (*insert_exchange_keys)(void *cls,
                             const char *exchange_url,
                             const struct TALER_EXCHANGE_Keys *keys,
                             struct GNUNET_TIME_Absolute first_retry,
                             uint32_t http_status,
                             enum TALER_ErrorCode ec);
 
 
   /**
    * Lookup all of the token families the given instance has configured.
    *
    * @param cls closure
    * @param instance_id instance to lookup token families for
    * @param cb function to call on all token families found
    * @param cb_cls closure for @a cb
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_token_families)(void *cls,
                              const char *instance_id,
                              TALER_MERCHANTDB_TokenFamiliesCallback cb,
                              void *cb_cls);
 
   /**
    * Lookup details about a particular token family.
    *
    * @param cls closure
    * @param instance_id instance to lookup token family for
    * @param token_family_slug token family to lookup
    * @param[out] details set to the token family details on success, can be NULL
    *             (in that case we only want to check if the token family exists)
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_token_family)(void *cls,
                            const char *instance_id,
                            const char *token_family_slug,
                            struct TALER_MERCHANTDB_TokenFamilyDetails *details);
 
   /**
    * Delete information about a token family.
    *
    * @param cls closure
    * @param instance_id instance to delete token family of
    * @param token_family_slug slug of token family to delete
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*delete_token_family)(void *cls,
                            const char *instance_id,
                            const char *token_family_slug);
 
   /**
    * Update details about a particular token family.
    *
    * @param cls closure
    * @param instance_id instance to update token family for
    * @param token_family_slug slug of token family to update
    * @param details set to the updated token family on success, can be NULL
    *        (in that case we only want to check if the token family exists)
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*update_token_family)(
     void *cls,
     const char *instance_id,
     const char *token_family_slug,
     const struct TALER_MERCHANTDB_TokenFamilyDetails *details);
 
 
   /**
    * Insert details about a particular token family.
    *
    * @param cls closure
    * @param instance_id instance to insert token family for
    * @param token_family_slug slug of token family to insert
    * @param details the token family details to insert
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*insert_token_family)(
     void *cls,
     const char *instance_id,
     const char *token_family_slug,
     const struct TALER_MERCHANTDB_TokenFamilyDetails *details);
 
 
   /**
   * Lookup details about a particular token family key.
   *
   * @param cls closure
   * @param instance_id instance to lookup token family key for
   * @param token_family_slug slug of token family to lookup
   * @param valid_at find a key with a validity period that includes this time
   * @param sign_until find a private key that can sign until this time
   * @param[out] details set to the token family key details on success, can be NULL
   *             (in that case we only want to check if the token family key exists)
   * @return database result code
   */
   enum GNUNET_DB_QueryStatus
     (*lookup_token_family_key)(
     void *cls,
     const char *instance_id,
     const char *token_family_slug,
     struct GNUNET_TIME_Timestamp valid_at,
     struct GNUNET_TIME_Timestamp sign_until,
     struct TALER_MERCHANTDB_TokenFamilyKeyDetails *details);
 
 
   /**
    * Lookup token family keys that may be used for a payment.
    *
    * @param cls closure
    * @param instance_id instance to lookup token family key for
    * @param token_family_slug slug of token family to lookup
    * @param start_time signature validity start the keys must fall into
    * @param end_time signature validity end the keys must fall into
    * @param cb function to call with each matching key
    * @param cb_cls closure for @a cb
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_token_family_keys)(
     void *cls,
     const char *instance_id,
     const char *token_family_slug,
     struct GNUNET_TIME_Timestamp start_time,
     struct GNUNET_TIME_Timestamp end_time,
     TALER_MERCHANTDB_TokenKeyCallback cb,
     void *cb_cls);
 
 
   /**
    * Insert details a key pair for a token family.
    *
    * @param cls closure
    * @param merchant_id instance name
    * @param token_family_slug slug of token family to insert the key pair for
    * @param pub token family public key
    * @param priv token family private key
    * @param key_expires when does the private key expire (because
    *     the validity period of the next token family key starts)
    * @param valid_after start of validity period for signatures with this key
    * @param valid_before end of validity period for signatures with this key
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*insert_token_family_key)(
     void *cls,
     const char *merchant_id,
     const char *token_family_slug,
     const struct TALER_TokenIssuePublicKey *pub,
     const struct TALER_TokenIssuePrivateKey *priv,
     struct GNUNET_TIME_Timestamp key_expires,
     struct GNUNET_TIME_Timestamp valid_after,
     struct GNUNET_TIME_Timestamp valid_before);
 
   /**
    * Lookup deposits that are finished and awaiting a wire transfer.
    *
    * @param cls closure
    * @param exchange_url exchange to filter deposits by
    * @param limit maximum number of deposits to return
    * @param allow_future true to allow deposits with wire deadline in the future
    * @param cb function to call with deposit data
    * @param cb_cls closure for @a cb
    * @return transaction status
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_pending_deposits)(
     void *cls,
     const char *exchange_url,
     uint64_t limit,
     bool allow_future,
     TALER_MERCHANTDB_PendingDepositsCallback cb,
     void *cb_cls);
 
 
   /**
    * Update the deposit confirmation status associated with
    * the given @a deposit_serial.
    *
    * @param cls closure
    * @param deposit_serial deposit to update status for
    * @param retry_needed true if the HTTP request should be retried
    * @param retry_time when should we ask the exchange again
    * @param last_http_status HTTP status code of the last reply
    * @param last_ec Taler error code of the last reply
    * @param last_detail detail from error message to record, possibly NULL
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*update_deposit_confirmation_status)(
     void *cls,
     uint64_t deposit_serial,
     bool retry_needed,
     struct GNUNET_TIME_Timestamp retry_time,
     uint32_t last_http_status,
     enum TALER_ErrorCode last_ec,
     const char *last_detail);
 
 
   /**
    * Update the amount of receipts for a Donau instance.
    *
    * @param cls closure
    * @param donau_instances_serial serial number of the Donau instance
    * @param new_amount new receipts_to_date amount
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*update_donau_instance_receipts_amount)(
     void *cls,
     uint64_t *donau_instances_serial,
     const struct TALER_Amount *new_amount
     );
 
 
   /**
    * Check if a new matching multi-factor authorization (MFA) challenge
    * exists in the database.
    *
    * @param cls closure
    * @param challenge_id set to the ID of the challenge
    * @param h_body hash of the request body
    * @param[out] salt salt used to compute @a h_body
    * @param[out] required address set to where the challenge is to be send
    * @param[out] op operation that triggered the MFA request
    * @param[out] confirmation_date when was the challenge solved,
    *             set to "GNUNET_TIME_ABSOLUTE_NEVER" if unsolved
    * @param[out] retransmission_date set to when a fresh challenge
    *             may be transmitted
    * @param[out] retry_counter set to the number of attempts that remain
    *             for solving the challenge (after this time)
    * @param[out] tan_channel which channel was used
    * @param[out] instance_name name of the instance for which the
    *             challenge is being issued
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_mfa_challenge)(
     void *cls,
     uint64_t challenge_id,
     const struct TALER_MERCHANT_MFA_BodyHash *h_body,
     struct TALER_MERCHANT_MFA_BodySalt *salt,
     char **required_address,
     enum TALER_MERCHANT_MFA_CriticalOperation *op,
     struct GNUNET_TIME_Absolute *confirmation_date,
     struct GNUNET_TIME_Absolute *retransmission_date,
     uint32_t *retry_counter,
     enum TALER_MERCHANT_MFA_Channel *tan_channel,
     char **instance_name);
 
 
   /**
    * Attempt to solve new multi-factor authorization (MFA) challenge.
    * Checks the solution against the code in the database and updates
    * the solution state and (on failure) retry counter depending on
    * the result.
    *
    * @param cls closure
    * @param challenge_id challenge ID to be solved
    * @param h_body body of the operation the challenge authorizes
    * @param solution proposed solution to be checked against the actual code
    * @param[out] solved set to true if the challenge was solved by
    *             @a solution
    * @param[out] retry_counter set to the number of attempts that remain
    *             for solving the challenge (after this time)
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*solve_mfa_challenge)(
     void *cls,
     uint64_t challenge_id,
     const struct TALER_MERCHANT_MFA_BodyHash *h_body,
     const char *solution,
     bool *solved,
     uint32_t *retry_counter);
 
 
   /**
    * Update the state of an MFA challenge as we have now
    * retransmitted the challenge code.
    *
    * @param cls closure
    * @param challenge_id challenge ID to be solved
    * @param code new challenge code
    * @param retry_counter number of attempts that remain
    *             for solving the challenge
    * @param expiration_date when should the challenge expire
    * @param retransmission_date set to when a fresh challenge
    *             may be transmitted next
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*update_mfa_challenge)(
     void *cls,
     uint64_t challenge_id,
     const char *code,
     uint32_t retry_counter,
     struct GNUNET_TIME_Absolute expiration_date,
     struct GNUNET_TIME_Absolute retransmission_date);
 
 
   /**
    * Create new multi-factor authorization (MFA) challenge in the database.
    *
    * @param cls closure
    * @param op operation that triggered the MFA request
    * @param h_body hash of the request body
    * @param salt salt used to compute @a h_body
    * @param code challenge code sent to the user
    * @param expiration_date when should the challenge expire
    * @param retansmission_date when do we next allow retransmission
    *        of the challenge
    * @param tan_channel which channel was used
    * @param required_address address
    *        where the challenge is to be sent
    * @param instance_id name of the instance for which the challenge
    *        is being created
    * @param[out] challenge_id set to the ID of the new challenge
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*create_mfa_challenge)(
     void *cls,
     enum TALER_MERCHANT_MFA_CriticalOperation op,
     const struct TALER_MERCHANT_MFA_BodyHash *h_body,
     const struct TALER_MERCHANT_MFA_BodySalt *salt,
     const char *code,
     struct GNUNET_TIME_Absolute expiration_date,
     struct GNUNET_TIME_Absolute retransmission_date,
     enum TALER_MERCHANT_MFA_Channel tan_channel,
     const char *required_address,
     const char *instance_id,
     uint64_t *challenge_id);
 
 
   /**
    * Insert information about a Donau instance.
    *
    * @param cls closure
    * @param donau_url URL of the Donau instance
    * @param charity details of the charity
    * @param charity_id charity ID of the Donau instance
    */
   enum GNUNET_DB_QueryStatus
     (*insert_donau_instance)(
     void *cls,
     const char *donau_url,
     const struct DONAU_Charity *charity,
     uint64_t charity_id
     );
 
 
   /**
    * Check if information about a Donau instance exists.
    *
    * @param cls closure
    * @param merchant_pub public key of the instance
    * @param donau_url URL of the Donau instance
    * @param charity_id charity ID of the Donau instance
    */
   enum GNUNET_DB_QueryStatus
     (*check_donau_instance)(
     void *cls,
     const struct TALER_MerchantPublicKeyP *merchant_pub,
     const char *donau_url,
     uint64_t charity_id
     );
 
   /**
    * Select donau instance by serial number.
    *
    * @param cls closure
    * @param serial serial number of the Donau instance in DB
    * @param[out] donau_url set to the URL of the Donau instance
    * @param[out] charity_id set to the charity ID of the Donau instance
    */
   enum GNUNET_DB_QueryStatus
     (*select_donau_instance_by_serial)(
     void *cls,
     uint64_t serial,
     char **donau_url,
     uint64_t *charity_id);
 
   /**
    * Select all Donau instances. Note that this callback only
    * returns Donau instances for which we have successfully
    * retrieved /keys.
    *
    * @param cls closure
    * @param id instance to restrict to
    * @param cb function to call on all Donau instances found
    * @param cb_cls closure for @a cb
    */
   enum GNUNET_DB_QueryStatus
     (*select_donau_instances)(
     void *cls,
     const char *id,
     TALER_MERCHANTDB_DonauInstanceCallback cb,
     void *cb_cls);
 
 
   /**
    * Select all Donau instances, regardless of instance and also
    * regardless of whether we got a /keys response.
    *
    * @param cls closure
    * @param cb function to call on all Donau instances found
    * @param cb_cls closure for @a cb
    */
   enum GNUNET_DB_QueryStatus
     (*select_all_donau_instances)(
     void *cls,
     TALER_MERCHANTDB_DonauInstanceCallback cb,
     void *cb_cls);
 
 
   /**
    * Select all Donau instances, but only the donau_url
    * and charity_max_per_year.
    *
    * @param cls closure
    * @param cb function to call on all Donau instances found
    * @param cb_cls closure for @a cb
    */
   enum GNUNET_DB_QueryStatus
     (*select_donau_instances_filtered)(
     void *cls,
     const char *currency,
     TALER_MERCHANTDB_DonauInstanceFilteredCallback cb,
     void *cb_cls);
 
   /**
    * Lookup Donau keys by URL.
    *
    * @param cls closure
    * @param donau_url URL of the Donau instance
    * @param[out] keys set to the Donau keys on success
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_donau_keys)(
     void *cls,
     const char *donau_url,
     struct GNUNET_TIME_Absolute *first_retry,
     struct DONAU_Keys **keys);
 
   /**
    * Lookup a Donau instance by its instance ID and URL.
    *
    * @param cls closure
    * @param instance_id instance ID of the Donau instance
    * @param donau_url URL of the Donau instance
    * @param charity_id set to the charity ID of the Donau instance
    * @param charity_priv set to the private key of the charity
    * @param charity_max_per_year set to the maximum amount
    *          the charity can receive per year
    * @param charity_receipts_to_date set to the total amount
    *         the charity has received to date
    * @param donau_keys_json set to the JSON representation of the
    *        Donau keys
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_order_charity)(
     void *cls,
     const char *instance_id,
     const char *donau_url,
     uint64_t *charity_id,
     struct DONAU_CharityPrivateKeyP *charity_priv,
     struct TALER_Amount *charity_max_per_year,
     struct TALER_Amount *charity_receipts_to_date,
     json_t **donau_keys_json,
     uint64_t *donau_instance_serial);
 
   /**
    * Upsert Donau keys into the database.
    *
    * @param cls closure
    * @param keys Donau keys to insert or update
    */
   enum GNUNET_DB_QueryStatus
     (*upsert_donau_keys)(
     void *cls,
     const struct DONAU_Keys *keys,
     struct GNUNET_TIME_Absolute first_retry);
 
   /**
    * Update information about a Donau instance.
    *
    * @param cls closure
    * @param donau_url URL of the Donau instance
    * @param charity details of the charity
    * @param charity_id charity ID of the Donau instance
    */
   enum GNUNET_DB_QueryStatus
     (*update_donau_instance)(
     void *cls,
     const char *donau_url,
     const struct DONAU_Charity *charity,
     uint64_t charity_id);
 
   /**
    * Delete information about a Donau instance.
    *
    * @param cls closure
    * @param charity_id charity ID of the Donau instance to delete
    */
   enum GNUNET_DB_QueryStatus
     (*delete_donau_instance)(
     void *cls,
     const char *id,
     uint64_t charity_id);
 
   /**
    * Lookup amount statistics for instance and slug by bucket.
    *
    * @param cls closure
    * @param instance_id instance to lookup statistics for
    * @param slug instance to lookup statistics for
    * @param cb function to call on all token families found
    * @param cb_cls closure for @a cb
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_statistics_amount_by_bucket)(
     void *cls,
     const char *instance_id,
     const char *slug,
     TALER_MERCHANTDB_AmountByBucketStatisticsCallback cb,
     void *cb_cls);
 
   /**
    * Lookup amount statistics for instance and slug by bucket,
    * restricting to a fixed number of buckets at a given granularity.
    *
    * @param cls closure
    * @param instance_id instance to lookup statistics for
    * @param slug instance to lookup statistics for
    * @param granularity limit to buckets of this size
    * @param counter requested number of buckets
    * @param cb function to call on all token families found
    * @param cb_cls closure for @a cb
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_statistics_amount_by_bucket2)(
     void *cls,
     const char *instance_id,
     const char *slug,
     const char *granularity,
     uint64_t counter,
     TALER_MERCHANTDB_AmountByBucketStatisticsCallback2 cb,
     void *cb_cls);
 
 
   /**
    * Lookup counter statistics for instance and slug by bucket.
    *
    * @param cls closure
    * @param instance_id instance to lookup statistics for
    * @param slug instance to lookup statistics for
    * @param cb function to call on all token families found
    * @param cb_cls closure for @a cb
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_statistics_counter_by_bucket)(
     void *cls,
     const char *instance_id,
     const char *slug,
     TALER_MERCHANTDB_CounterByBucketStatisticsCallback cb,
     void *cb_cls);
 
   /**
    * Lookup counter statistics for instance and slug-prefix by bucket.
    *
    * @param cls closure
    * @param instance_id instance to lookup statistics for
    * @param prefix slug prefix to lookup statistics under
    * @param granularity limit to buckets of this size
    * @param counter requested number of buckets
    * @param cb function to call on all token families found
    * @param cb_cls closure for @a cb
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_statistics_counter_by_bucket2)(
     void *cls,
     const char *instance_id,
     const char *prefix,
     const char *granularity,
     uint64_t counter,
     TALER_MERCHANTDB_CounterByBucketStatisticsCallback2 cb,
     void *cb_cls);
 
 
   /**
    * Lookup amount statistics for instance and slug by interval.
    *
    * @param cls closure
    * @param instance_id instance to lookup statistics for
    * @param slug instance to lookup statistics for
    * @param cb function to call on all token families found
    * @param cb_cls closure for @a cb
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_statistics_amount_by_interval)(
     void *cls,
     const char *instance_id,
     const char *slug,
     TALER_MERCHANTDB_AmountByIntervalStatisticsCallback cb,
     void *cb_cls);
 
   /**
    * Lookup counter statistics for instance and slug by interval.
    *
    * @param cls closure
    * @param instance_id instance to lookup statistics for
    * @param slug instance to lookup statistics for
    * @param cb function to call on all token families found
    * @param cb_cls closure for @a cb
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_statistics_counter_by_interval)(
     void *cls,
     const char *instance_id,
     const char *slug,
     TALER_MERCHANTDB_CounterByIntervalStatisticsCallback cb,
     void *cb_cls);
 
 
   /**
    * Lookup all of the money pots the given instance has configured.
    *
    * @param cls closure
    * @param instance_id instance to lookup money pots for
    * @param limit number of entries to return, negative for descending in execution time,
    *                positive for ascending in execution time
    * @param offset number of the money pot we want to offset from
    * @param cb function to call on all money pots found
    * @param cb_cls closure for @a cb
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*select_money_pots)(void *cls,
                          const char *instance_id,
                          int64_t limit,
                          uint64_t offset,
                          TALER_MERCHANTDB_MoneyPotsCallback cb,
                          void *cb_cls);
 
 
   /**
    * Check that all of the money pots given exist at the instance,
    * returning one that does *not* exist (for generating an error)
    * if the check fails.
    *
    * @param cls closure
    * @param instance_id instance to lookup token families for
    * @param pots_len length of the @a pots array
    * @param pots money pot identifiers to check if they exist
    * @param[out] pot_missing set to ID of pot not known at the instance
    * @return transaction status,
    *   #GNUNET_DB_STATUS_SUCCESS_NO_RESULTS means that all pots exist
    *   #GNUNET_DB_STATUS_SUCCESS_ONE_RESULT indicates that
    *       @a pot_missing was initialized to a missing pot
    */
   enum GNUNET_DB_QueryStatus
     (*check_money_pots)(void *cls,
                         const char *instance_id,
                         unsigned int pots_len,
                         uint64_t pots[static pots_len],
                         uint64_t *pot_missing);
 
   /**
    * Lookup details about a particular money pot.
    *
    * @param cls closure
    * @param instance_id instance to lookup money pot for
    * @param money_pot_id serial number of the pot to lookup
    * @param [out] name set to name of the pot,
    *         must be freed by caller
    * @param[out] description set to description of the pot,
    *         must be freed by caller
    * @param[out] pot_total_len set to length of @a pot_totals array
    * @param[out] pot_totals set to amounts currently in the pot;
    *         array must be freed by caller
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*select_money_pot)(void *cls,
                         const char *instance_id,
                         uint64_t money_pot_id,
                         char **name,
                         char **description,
                         size_t *pot_total_len,
                         struct TALER_Amount **pot_totals);
 
   /**
    * Delete information about a money pot.
    *
    * @param cls closure
    * @param instance_id instance to delete money pot of
    * @param money_pot_id serial number of the pot to delete
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*delete_money_pot)(void *cls,
                         const char *instance_id,
                         uint64_t money_pot_id);
 
   /**
    * Update details about a particular money pot.
    *
    * @param cls closure
    * @param instance_id instance to update money pot for
    * @param money_pot_id serial number of the pot to delete
    * @param name set to name of the pot
    * @param description set to description of the pot
    * @param opt_len length of @a old_pot_totals
    * @param old_pot_totals amounts expected currently in the pot,
    *        NULL to not check (non-NULL but @a opt_len=0 checks for [])
    * @param npt_len length of @a new_pot_totals
    * @param new_pot_totals new amounts in the pot,
    *        NULL to not update (non-NULL but @a npt_len=0 resets to [])
    * @param[out] conflict_total set to true if @a old_pot_total does not match
    * @param[out] conflict_name set to true if @a name is used by another pot
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*update_money_pot)(
     void *cls,
     const char *instance_id,
     uint64_t money_pot_id,
     const char *name,
     const char *description,
     size_t opt_len,
     const struct TALER_Amount *old_pot_totals,
     size_t npt_len,
     const struct TALER_Amount *new_pot_totals,
     bool *conflict_total,
     bool *conflict_name);
 
 
   /**
    * Increment amounts in money pots.  If a money pot does not exist,
    * it is simply skipped (without causing an error!).
    *
    * @param cls closure
    * @param instance_id instance to update money pot for
    * @param money_pots_len length of the @a money_pots_ids
    *        and @a pot_increments arrays
    * @param money_pot_ids serial numbers of the pots to increment
    * @param pot_increments new amounts to add to the respective pot
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*increment_money_pots)(
     void *cls,
     const char *instance_id,
     size_t money_pots_len,
     const uint64_t *money_pot_ids,
     const struct TALER_Amount *pot_increments);
 
 
   /**
    * Insert details about a particular pot.
    *
    * @param cls closure
    * @param instance_id instance to insert pot for
    * @param name set to name of the pot
    * @param description set to description of the pot
    * @param[out] money_pot_id serial number of the new pot
    * @return database result code, #GNUNET_DB_STATUS_SUCCESS_NO_RESULTS
    *   on conflict (@a name already in use at @a instance_id).
    */
   enum GNUNET_DB_QueryStatus
     (*insert_money_pot)(
     void *cls,
     const char *instance_id,
     const char *name,
     const char *description,
     uint64_t *money_pot_id);
 
   // Reports
 
   /**
    * Lookup all of the reports the given instance has configured.
    *
    * @param cls closure
    * @param instance_id instance to lookup reports for
    * @param limit number of entries to return, negative for descending in execution time,
    *                positive for ascending in execution time
    * @param offset expected_transfer_serial number of the transfer we want to offset from
    * @param cb function to call on all reports found
    * @param cb_cls closure for @a cb
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*select_reports)(void *cls,
                       const char *instance_id,
                       int64_t limit,
                       uint64_t offset,
                       TALER_MERCHANTDB_ReportsCallback cb,
                       void *cb_cls);
 
 
   /**
    * Lookup all of the reports pending for the given backend.
    *
    * @param cls closure
    * @param cb function to call on all reports found
    * @param cb_cls closure for @a cb
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*lookup_reports_pending)(void *cls,
                               TALER_MERCHANTDB_ReportsPendingCallback cb,
                               void *cb_cls);
 
   /**
    * Lookup details about a particular report.
    *
    * @param cls closure
    * @param instance_id instance to lookup reports for
    * @param report_id serial number of the report to lookup
    * @param[out] report_program_section configuration section of program
    *   for report generation
    * @param[out] report_description text describing the report
    * @param[out] mime_type mime type to request from the @a data_source
    * @param[out] data_source relative URL (to instance base URL)
    *   to request report data from
    * @param[out] target_address where to send report data
    * @param[out] frequency report frequency
    * @param[out] frequency_shift how much to shift the report time from a
    *   multiple of the report @a frequency
    * @param[out] next_transmission when will the report be generated next
    * @param[out] last_error_code status of the last report
    * @param[out] last_error_detail details about failures of last generation
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*select_report)(void *cls,
                      const char *instance_id,
                      uint64_t report_id,
                      char **report_program_section,
                      char **report_description,
                      char **mime_type,
                      char **data_source,
                      char **target_address,
                      struct GNUNET_TIME_Relative *frequency,
                      struct GNUNET_TIME_Relative *frequency_shift,
                      struct GNUNET_TIME_Absolute *next_transmission,
                      enum TALER_ErrorCode *last_error_code,
                      char **last_error_detail);
 
   /**
    * Check that a particular report is scheduled under the
    * given @a report_id and @a report_token. Does not
    * validate that the report is actually due.
    *
    * @param cls closure
    * @param report_id serial number of the report to lookup
    * @param report_token report token to check
    * @param mime_type mime type to request from the @a data_source
    * @param[out] instance_id instance to lookup reports for
    * @param[out] data_source relative URL (to instance base URL)
    *   to request report data from
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*check_report)(void *cls,
                     uint64_t report_id,
                     const struct TALER_MERCHANT_ReportToken *report_token,
                     const char *mime_type,
                     char **instance_id,
                     char **data_source);
 
 
   /**
    * Delete information about a report.
    *
    * @param cls closure
    * @param instance_id instance to delete report of
    * @param report_id serial number of the pot to delete
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*delete_report)(void *cls,
                      const char *instance_id,
                      uint64_t report_id);
 
   /**
    * Update transmission status about a particular report.
    *
    * @param cls closure
    * @param instance_id instance to update report for
    * @param report_id serial number of the pot to update
    * @param next_tranmission when should the report be generated next
    * @param last_error_code #TALER_EC_NONE on success
    * @param last_error_detail NULL on success
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*update_report_status)(
     void *cls,
     const char *instance_id,
     uint64_t report_id,
     struct GNUNET_TIME_Timestamp next_transmission,
     enum TALER_ErrorCode last_error_code,
     const char *last_error_detail);
 
 
   /**
    * Update details about a particular report.
    *
    * @param cls closure
    * @param instance_id instance to update report for
    * @param report_id serial number of the report to update
    * @param report_program_section configuration section of program
    *   for report generation
    * @param report_description text describing the report
    * @param mime_type mime type to request from the @a data_source
    * @param data_source relative URL (to instance base URL)
    *   to request report data from
    * @param target_address where to send report data
    * @param frequency report frequency
    * @param frequency_shift how much to shift the report time from a
    *   multiple of the report @a frequency
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*update_report)(
     void *cls,
     const char *instance_id,
     uint64_t report_id,
     const char *report_program_section,
     const char *report_description,
     const char *mime_type,
     const char *data_source,
     const char *target_address,
     struct GNUNET_TIME_Relative frequency,
     struct GNUNET_TIME_Relative frequency_shift);
 
 
   /**
    * Insert details about a particular report.
    *
    * @param cls closure
    * @param instance_id instance to insert report for
    * @param report_program_section configuration section of program
    *   for report generation
    * @param report_description text describing the report
    * @param mime_type mime type to request from the @a data_source
    * @param data_source relative URL (to instance base URL)
    *   to request report data from
    * @param target_address where to send report data
    * @param frequency report frequency
    * @param frequency_shift how much to shift the report time from a
    *   multiple of the report @a frequency
    * @param[out] report_id serial number of the new pot
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*insert_report)(
     void *cls,
     const char *instance_id,
     const char *report_program_section,
     const char *report_description,
     const char *mime_type,
     const char *data_source,
     const char *target_address,
     struct GNUNET_TIME_Relative frequency,
     struct GNUNET_TIME_Relative frequency_shift,
     uint64_t *report_id);
 
 
   // groups
 
   /**
    * Lookup all of the product groups the given instance has configured.
    *
    * @param cls closure
    * @param instance_id instance to lookup product groups for
    * @param limit number of entries to return, negative for descending in execution time,
    *                positive for ascending in execution time
    * @param offset expected_transfer_serial number of the transfer we want to offset from
    * @param cb function to call on all groups found
    * @param cb_cls closure for @a cb
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*select_product_groups)(void *cls,
                              const char *instance_id,
                              int64_t limit,
                              uint64_t offset,
                              TALER_MERCHANTDB_ProductGroupsCallback cb,
                              void *cb_cls);
 
   /**
    * Delete information about a product group.
    *
    * @param cls closure
    * @param instance_id instance to delete product group of
    * @param product_group_id serial number of the group to delete
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*delete_product_group)(void *cls,
                             const char *instance_id,
                             uint64_t product_group_id);
 
   /**
    * Update details about a particular product group.
    *
    * @param cls closure
    * @param instance_id instance to update product group for
    * @param product_group_id serial number of the group to update
    * @param name set to name of the group
    * @param description set to description of the group
    * @param[out] conflict set to true if @a name is already used
    * @return database result code
    */
   enum GNUNET_DB_QueryStatus
     (*update_product_group)(
     void *cls,
     const char *instance_id,
     uint64_t product_group_id,
     const char *name,
     const char *description,
     bool *conflict);
 
 
   /**
    * Insert details about a particular product group.
    *
    * @param cls closure
    * @param instance_id instance to insert group for
    * @param name set to name of the group
    * @param description set to description of the group
    * @param[out] product_group_id serial number of the new group
    * @return database result code, #GNUNET_DB_STATUS_SUCCESS_NO_RESULTS
    *   on conflict (@a name already in use at @a instance_id).
    */
   enum GNUNET_DB_QueryStatus
     (*insert_product_group)(
     void *cls,
     const char *instance_id,
     const char *name,
     const char *description,
     uint64_t *product_group_id);
 
 };
 
 #endif