Increase perf of read/write locks

changelog.d/16149.misc

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+Increase performance of read/write locks.

synapse/storage/schema/main/delta/80/02_read_write_locks_unlogged.sql.postgres

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+/* Copyright 2023 The Matrix.org Foundation C.I.C
+ *
+ * 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.
+ */
+
+-- Mark the worker_read_write_locks* tables as UNLOGGED, to increase
+-- performance. This means that we don't replicate the tables, and they get
+-- truncated on a crash. This is acceptable as a) in those cases it's likely
+-- that Synapse needs to be stopped/restarted anyway, and b) the locks are
+-- considered best-effort anyway.
+
+-- We need to remove and recreate the circular foreign key references, as
+-- UNLOGGED tables can't reference normal tables.
+ALTER TABLE worker_read_write_locks_mode DROP CONSTRAINT IF EXISTS worker_read_write_locks_mode_foreign;
+
+ALTER TABLE worker_read_write_locks SET UNLOGGED;
+ALTER TABLE worker_read_write_locks_mode SET UNLOGGED;
+
+ALTER TABLE worker_read_write_locks_mode ADD CONSTRAINT worker_read_write_locks_mode_foreign
+    FOREIGN KEY (lock_name, lock_key, token) REFERENCES worker_read_write_locks(lock_name, lock_key, token) DEFERRABLE INITIALLY DEFERRED;