Fix error on sqlite 3.7

Create the url_cache index on local_media_repository as a background update, so
that we can detect whether we are on sqlite or not and create a partial or
complete index accordingly.

To avoid running the cleanup job before we have built the index, add a bailout
which will defer the cleanup if the bg updates are still running.

Fixes https://github.com/matrix-org/synapse/issues/2572.

2 files changed, 28 insertions, 1 deletions

diff --git a/synapse/storage/schema/delta/44/expire_url_cache.sql b/synapse/storage/schema/delta/44/expire_url_cache.sql
index e2b775f038..b12f9b2ebf 100644
--- a/synapse/storage/schema/delta/44/expire_url_cache.sql
+++ b/synapse/storage/schema/delta/44/expire_url_cache.sql
@@ -13,7 +13,10 @@
  * limitations under the License.
  */
 
-CREATE INDEX local_media_repository_url_idx ON local_media_repository(created_ts) WHERE url_cache IS NOT NULL;
+-- this didn't work on SQLite 3.7 (because of lack of partial indexes), so was
+-- removed and replaced with 46/local_media_repository_url_idx.sql.
+--
+-- CREATE INDEX local_media_repository_url_idx ON local_media_repository(created_ts) WHERE url_cache IS NOT NULL;
 
 -- we need to change `expires` to `expires_ts` so that we can index on it. SQLite doesn't support
 -- indices on expressions until 3.9.
diff --git a/synapse/storage/schema/delta/46/local_media_repository_url_idx.sql b/synapse/storage/schema/delta/46/local_media_repository_url_idx.sql
new file mode 100644
index 0000000000..bbfc7f5d1a
--- /dev/null
+++ b/synapse/storage/schema/delta/46/local_media_repository_url_idx.sql
@@ -0,0 +1,24 @@
+/* Copyright 2017 New Vector Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+-- register a background update which will recreate the
+-- local_media_repository_url_idx index.
+--
+-- We do this as a bg update not because it is a particularly onerous
+-- operation, but because we'd like it to be a partial index if possible, and
+-- the background_index_update code will understand whether we are on
+-- postgres or sqlite and behave accordingly.
+INSERT INTO background_updates (update_name, progress_json) VALUES
+    ('local_media_repository_url_idx', '{}');