[datastore] Fix #3743

This change adds support for key == NULL to the datastore plugins
and replaces the offset argument with a next_uid and random arguments to
increase performance in the key == NULL case.

With the offset argument a datastore plugin would have to count all
matching keys before fetching the key at the right offset, which would
iterate over the entire database in the case of key == NULL.

The offset argument was used in two ways: to iterate over a set of
matching values and to start iteration at a random matching value. The new API
seperates these into two arguments: if random is true it will return a
random matching value, otherwise next_uid can be set to uid + 1 to return the
next matching value.

The random argument was not added to get_zero_anonymity. This function
is used to periodically insert zero anonymity values into the DHT. I
don't think it's necessary to randomize this.

1 files changed, 7 insertions, 6 deletions

diff --git a/src/fs/gnunet-service-fs_cadet_server.c b/src/fs/gnunet-service-fs_cadet_server.c
index b1a098175..f8619b812 100644
--- a/src/fs/gnunet-service-fs_cadet_server.c
+++ b/src/fs/gnunet-service-fs_cadet_server.c
@@ -345,12 +345,13 @@ handle_request (void *cls,
                             GNUNET_NO);
   refresh_timeout_task (sc);
   sc->qe = GNUNET_DATASTORE_get_key (GSF_dsh,
-                                     0,
-                                     &sqm->query,
-                                     ntohl (sqm->type),
-                                     0 /* priority */,
-                                     GSF_datastore_queue_size,
-                                     &handle_datastore_reply,
+                                     0 /* next_uid */,
+                                     false /* random */,
+                                     &sqm->query,
+                                     ntohl (sqm->type),
+                                     0 /* priority */,
+                                     GSF_datastore_queue_size,
+                                     &handle_datastore_reply,
                                      sc);
   if (NULL == sc->qe)
   {