Add a partial index to `presence_stream` to speed up startups (#10748)

Signed-off-by: Sean Quah <seanq@element.io>

changelog.d/10748.misc

@@ -0,0 +1 @@
+Add an index to `presence_stream` to hopefully speed up startups a little.

scripts/synapse_port_db

@@ -46,6 +46,7 @@ from synapse.storage.databases.main.events_bg_updates import (
 from synapse.storage.databases.main.media_repository import (
     MediaRepositoryBackgroundUpdateStore,
 )
+from synapse.storage.databases.main.presence import PresenceBackgroundUpdateStore
 from synapse.storage.databases.main.pusher import PusherWorkerStore
 from synapse.storage.databases.main.registration import (
     RegistrationBackgroundUpdateStore,
@@ -179,6 +180,7 @@ class Store(
     EndToEndKeyBackgroundStore,
     StatsStore,
     PusherWorkerStore,
+    PresenceBackgroundUpdateStore,
 ):
     def execute(self, f, *args, **kwargs):
         return self.db_pool.runInteraction(f.__name__, f, *args, **kwargs)

synapse/storage/databases/main/presence.py

@@ -29,7 +29,26 @@ if TYPE_CHECKING:
     from synapse.server import HomeServer
 
 
-class PresenceStore(SQLBaseStore):
+class PresenceBackgroundUpdateStore(SQLBaseStore):
+    def __init__(
+        self,
+        database: DatabasePool,
+        db_conn: Connection,
+        hs: "HomeServer",
+    ):
+        super().__init__(database, db_conn, hs)
+
+        # Used by `PresenceStore._get_active_presence()`
+        self.db_pool.updates.register_background_index_update(
+            "presence_stream_not_offline_index",
+            index_name="presence_stream_state_not_offline_idx",
+            table="presence_stream",
+            columns=["state"],
+            where_clause="state != 'offline'",
+        )
+
+
+class PresenceStore(PresenceBackgroundUpdateStore):
     def __init__(
         self,
         database: DatabasePool,
@@ -332,6 +351,8 @@ class PresenceStore(SQLBaseStore):
         the appropriate time outs.
         """
 
+        # The `presence_stream_state_not_offline_idx` index should be used for this
+        # query.
         sql = (
             "SELECT user_id, state, last_active_ts, last_federation_update_ts,"
             " last_user_sync_ts, status_msg, currently_active FROM presence_stream"

synapse/storage/schema/main/delta/63/04add_presence_stream_not_offline_index.sql

@@ -0,0 +1,18 @@
+/*
+ * Copyright 2021 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.
+ */
+
+INSERT INTO background_updates (ordering, update_name, progress_json) VALUES
+  (6304, 'presence_stream_not_offline_index', '{}');