Remove check current state membership up to date (#13745)

* Remove checks for membership column in current_state_events
* Add schema script to force through the
  `current_state_events_membership` background job

Contributed by Nick @ Beeper (@fizzadar).

3 files changed, 100 insertions, 155 deletions

diff --git a/changelog.d/13745.misc b/changelog.d/13745.misc
new file mode 100644
index 0000000000..e97a789c0e
--- /dev/null
+++ b/changelog.d/13745.misc
@@ -0,0 +1 @@
+Remove old queries to join room memberships to current state events. Contributed by Nick @ Beeper (@fizzadar).
diff --git a/synapse/storage/databases/main/roommember.py b/synapse/storage/databases/main/roommember.py
index 6e1ff5626b..fdb4684e12 100644
--- a/synapse/storage/databases/main/roommember.py
+++ b/synapse/storage/databases/main/roommember.py
@@ -32,10 +32,7 @@ import attr
 
 from synapse.api.constants import EventTypes, Membership
 from synapse.metrics import LaterGauge
-from synapse.metrics.background_process_metrics import (
-    run_as_background_process,
-    wrap_as_background_process,
-)
+from synapse.metrics.background_process_metrics import wrap_as_background_process
 from synapse.storage._base import SQLBaseStore, db_to_json, make_in_list_sql_clause
 from synapse.storage.database import (
     DatabasePool,
@@ -91,16 +88,6 @@ class RoomMemberWorkerStore(EventsWorkerStore):
         # at a time. Keyed by room_id.
         self._joined_host_linearizer = Linearizer("_JoinedHostsCache")
 
-        # Is the current_state_events.membership up to date? Or is the
-        # background update still running?
-        self._current_state_events_membership_up_to_date = False
-
-        txn = db_conn.cursor(
-            txn_name="_check_safe_current_state_events_membership_updated"
-        )
-        self._check_safe_current_state_events_membership_updated_txn(txn)
-        txn.close()
-
         if (
             self.hs.config.worker.run_background_tasks
             and self.hs.config.metrics.metrics_flags.known_servers
@@ -157,34 +144,6 @@ class RoomMemberWorkerStore(EventsWorkerStore):
         self._known_servers_count = max([count, 1])
         return self._known_servers_count
 
-    def _check_safe_current_state_events_membership_updated_txn(
-        self, txn: LoggingTransaction
-    ) -> None:
-        """Checks if it is safe to assume the new current_state_events
-        membership column is up to date
-        """
-
-        pending_update = self.db_pool.simple_select_one_txn(
-            txn,
-            table="background_updates",
-            keyvalues={"update_name": _CURRENT_STATE_MEMBERSHIP_UPDATE_NAME},
-            retcols=["update_name"],
-            allow_none=True,
-        )
-
-        self._current_state_events_membership_up_to_date = not pending_update
-
-        # If the update is still running, reschedule to run.
-        if pending_update:
-            self._clock.call_later(
-                15.0,
-                run_as_background_process,
-                "_check_safe_current_state_events_membership_updated",
-                self.db_pool.runInteraction,
-                "_check_safe_current_state_events_membership_updated",
-                self._check_safe_current_state_events_membership_updated_txn,
-            )
-
     @cached(max_entries=100000, iterable=True)
     async def get_users_in_room(self, room_id: str) -> List[str]:
         """
@@ -212,31 +171,14 @@ class RoomMemberWorkerStore(EventsWorkerStore):
         `get_current_hosts_in_room()` and so we can re-use the cache but it's
         not horrible to have here either.
         """
-        # If we can assume current_state_events.membership is up to date
-        # then we can avoid a join, which is a Very Good Thing given how
-        # frequently this function gets called.
-        if self._current_state_events_membership_up_to_date:
-            sql = """
-                SELECT c.state_key FROM current_state_events as c
-                /* Get the depth of the event from the events table */
-                INNER JOIN events AS e USING (event_id)
-                WHERE c.type = 'm.room.member' AND c.room_id = ? AND membership = ?
-                /* Sorted by lowest depth first */
-                ORDER BY e.depth ASC;
-            """
-        else:
-            sql = """
-                SELECT c.state_key FROM room_memberships as m
-                /* Get the depth of the event from the events table */
-                INNER JOIN events AS e USING (event_id)
-                INNER JOIN current_state_events as c
-                ON m.event_id = c.event_id
-                AND m.room_id = c.room_id
-                AND m.user_id = c.state_key
-                WHERE c.type = 'm.room.member' AND c.room_id = ? AND m.membership = ?
-                /* Sorted by lowest depth first */
-                ORDER BY e.depth ASC;
-            """
+        sql = """
+            SELECT c.state_key FROM current_state_events as c
+            /* Get the depth of the event from the events table */
+            INNER JOIN events AS e USING (event_id)
+            WHERE c.type = 'm.room.member' AND c.room_id = ? AND membership = ?
+            /* Sorted by lowest depth first */
+            ORDER BY e.depth ASC;
+        """
 
         txn.execute(sql, (room_id, Membership.JOIN))
         return [r[0] for r in txn]
@@ -353,28 +295,14 @@ class RoomMemberWorkerStore(EventsWorkerStore):
             # We do this all in one transaction to keep the cache small.
             # FIXME: get rid of this when we have room_stats
 
-            # If we can assume current_state_events.membership is up to date
-            # then we can avoid a join, which is a Very Good Thing given how
-            # frequently this function gets called.
-            if self._current_state_events_membership_up_to_date:
-                # Note, rejected events will have a null membership field, so
-                # we we manually filter them out.
-                sql = """
-                    SELECT count(*), membership FROM current_state_events
-                    WHERE type = 'm.room.member' AND room_id = ?
-                        AND membership IS NOT NULL
-                    GROUP BY membership
-                """
-            else:
-                sql = """
-                    SELECT count(*), m.membership FROM room_memberships as m
-                    INNER JOIN current_state_events as c
-                    ON m.event_id = c.event_id
-                    AND m.room_id = c.room_id
-                    AND m.user_id = c.state_key
-                    WHERE c.type = 'm.room.member' AND c.room_id = ?
-                    GROUP BY m.membership
-                """
+            # Note, rejected events will have a null membership field, so
+            # we we manually filter them out.
+            sql = """
+                SELECT count(*), membership FROM current_state_events
+                WHERE type = 'm.room.member' AND room_id = ?
+                    AND membership IS NOT NULL
+                GROUP BY membership
+            """
 
             txn.execute(sql, (room_id,))
             res: Dict[str, MemberSummary] = {}
@@ -383,30 +311,18 @@ class RoomMemberWorkerStore(EventsWorkerStore):
 
             # we order by membership and then fairly arbitrarily by event_id so
             # heroes are consistent
-            if self._current_state_events_membership_up_to_date:
-                # Note, rejected events will have a null membership field, so
-                # we we manually filter them out.
-                sql = """
-                    SELECT state_key, membership, event_id
-                    FROM current_state_events
-                    WHERE type = 'm.room.member' AND room_id = ?
-                        AND membership IS NOT NULL
-                    ORDER BY
-                        CASE membership WHEN ? THEN 1 WHEN ? THEN 2 ELSE 3 END ASC,
-                        event_id ASC
-                    LIMIT ?
-                """
-            else:
-                sql = """
-                    SELECT c.state_key, m.membership, c.event_id
-                    FROM room_memberships as m
-                    INNER JOIN current_state_events as c USING (room_id, event_id)
-                    WHERE c.type = 'm.room.member' AND c.room_id = ?
-                    ORDER BY
-                        CASE m.membership WHEN ? THEN 1 WHEN ? THEN 2 ELSE 3 END ASC,
-                        c.event_id ASC
-                    LIMIT ?
-                """
+            # Note, rejected events will have a null membership field, so
+            # we we manually filter them out.
+            sql = """
+                SELECT state_key, membership, event_id
+                FROM current_state_events
+                WHERE type = 'm.room.member' AND room_id = ?
+                    AND membership IS NOT NULL
+                ORDER BY
+                    CASE membership WHEN ? THEN 1 WHEN ? THEN 2 ELSE 3 END ASC,
+                    event_id ASC
+                LIMIT ?
+            """
 
             # 6 is 5 (number of heroes) plus 1, in case one of them is the calling user.
             txn.execute(sql, (room_id, Membership.JOIN, Membership.INVITE, 6))
@@ -649,27 +565,15 @@ class RoomMemberWorkerStore(EventsWorkerStore):
         # We use `current_state_events` here and not `local_current_membership`
         # as a) this gets called with remote users and b) this only gets called
         # for rooms the server is participating in.
-        if self._current_state_events_membership_up_to_date:
-            sql = """
-                SELECT room_id, e.instance_name, e.stream_ordering
-                FROM current_state_events AS c
-                INNER JOIN events AS e USING (room_id, event_id)
-                WHERE
-                    c.type = 'm.room.member'
-                    AND c.state_key = ?
-                    AND c.membership = ?
-            """
-        else:
-            sql = """
-                SELECT room_id, e.instance_name, e.stream_ordering
-                FROM current_state_events AS c
-                INNER JOIN room_memberships AS m USING (room_id, event_id)
-                INNER JOIN events AS e USING (room_id, event_id)
-                WHERE
-                    c.type = 'm.room.member'
-                    AND c.state_key = ?
-                    AND m.membership = ?
-            """
+        sql = """
+            SELECT room_id, e.instance_name, e.stream_ordering
+            FROM current_state_events AS c
+            INNER JOIN events AS e USING (room_id, event_id)
+            WHERE
+                c.type = 'm.room.member'
+                AND c.state_key = ?
+                AND c.membership = ?
+        """
 
         txn.execute(sql, (user_id, Membership.JOIN))
         return frozenset(
@@ -707,27 +611,15 @@ class RoomMemberWorkerStore(EventsWorkerStore):
             user_ids,
         )
 
-        if self._current_state_events_membership_up_to_date:
-            sql = f"""
-                SELECT c.state_key, room_id, e.instance_name, e.stream_ordering
-                FROM current_state_events AS c
-                INNER JOIN events AS e USING (room_id, event_id)
-                WHERE
-                    c.type = 'm.room.member'
-                    AND c.membership = ?
-                    AND {clause}
-            """
-        else:
-            sql = f"""
-                SELECT c.state_key, room_id, e.instance_name, e.stream_ordering
-                FROM current_state_events AS c
-                INNER JOIN room_memberships AS m USING (room_id, event_id)
-                INNER JOIN events AS e USING (room_id, event_id)
-                WHERE
-                    c.type = 'm.room.member'
-                    AND m.membership = ?
-                    AND {clause}
-            """
+        sql = f"""
+            SELECT c.state_key, room_id, e.instance_name, e.stream_ordering
+            FROM current_state_events AS c
+            INNER JOIN events AS e USING (room_id, event_id)
+            WHERE
+                c.type = 'm.room.member'
+                AND c.membership = ?
+                AND {clause}
+        """
 
         txn.execute(sql, [Membership.JOIN] + args)
 
diff --git a/synapse/storage/schema/main/delta/72/07force_update_current_state_events_membership.py b/synapse/storage/schema/main/delta/72/07force_update_current_state_events_membership.py
new file mode 100644
index 0000000000..b5853d125c
--- /dev/null
+++ b/synapse/storage/schema/main/delta/72/07force_update_current_state_events_membership.py
@@ -0,0 +1,52 @@
+# Copyright 2022 Beeper
+#
+# 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.
+
+
+"""
+Forces through the `current_state_events_membership` background job so checks
+for its completion can be removed.
+
+Note the background job must still remain defined in the database class.
+"""
+
+
+def run_upgrade(cur, database_engine, *args, **kwargs):
+    cur.execute("SELECT update_name FROM background_updates")
+    rows = cur.fetchall()
+    for row in rows:
+        if row[0] == "current_state_events_membership":
+            break
+    # No pending background job so nothing to do here
+    else:
+        return
+
+    # Populate membership field for all current_state_events, this may take
+    # a while but was originally handled via a background update in 2019.
+    cur.execute(
+        """
+        UPDATE current_state_events
+        SET membership = (
+            SELECT membership FROM room_memberships
+            WHERE event_id = current_state_events.event_id
+        )
+        """
+    )
+
+    # Finally, delete the background job because we've handled it above
+    cur.execute(
+        """
+        DELETE FROM background_updates
+        WHERE update_name = 'current_state_events_membership'
+        """
+    )