Sliding Sync: Fix outlier re-persisting causing problems with sliding sync tables

changelog.d/17635.misc

@@ -0,0 +1 @@
+Pre-populate room data used in experimental [MSC3575](https://github.com/matrix-org/matrix-spec-proposals/pull/3575) Sliding Sync `/sync` endpoint for quick filtering/sorting.

synapse/storage/databases/main/events.py

@@ -163,24 +163,22 @@ class SlidingSyncMembershipInfo:
     sender: str
     membership_event_id: str
     membership: str
+
+
+@attr.s(slots=True, auto_attribs=True)
+class SlidingSyncMembershipInfoWithEventPos(SlidingSyncMembershipInfo):
+    """
+    SlidingSyncMembershipInfo + `stream_ordering`/`instance_name` of the membership
+    event
+    """
+
     membership_event_stream_ordering: int
     membership_event_instance_name: str
 
 
 @attr.s(slots=True, auto_attribs=True)
 class SlidingSyncTableChanges:
     room_id: str
-    # `stream_ordering` of the most recent event being persisted in the room. This doesn't
-    # need to be perfect, we just need *some* answer that points to a real event in the
-    # room in case we are the first ones inserting into the `sliding_sync_joined_rooms`
-    # table because of the `NON NULL` constraint on `event_stream_ordering`. In reality,
-    # `_update_sliding_sync_tables_with_new_persisted_events_txn()` is run after
-    # `_update_current_state_txn()` whenever a new event is persisted to update it to the
-    # correct latest value.
-    #
-    # This should be *some* value that points to a real event in the room if we are
-    # still joined to the room and some state is changing (`to_insert` or `to_delete`).
-    joined_room_best_effort_most_recent_stream_ordering: Optional[int]
     # If the row doesn't exist in the `sliding_sync_joined_rooms` table, we need to
     # fully-insert it which means we also need to include a `bump_stamp` value to use
     # for the row. This should only be populated when we're trying to fully-insert a
@@ -401,6 +399,9 @@ async def _calculate_sliding_sync_table_changes(
                 `stream_ordering`).
             delta_state: Deltas that are going to be used to update the
                 `current_state_events` table. Changes to the current state of the room.
+
+        Returns:
+            SlidingSyncTableChanges
         """
         to_insert = delta_state.to_insert
         to_delete = delta_state.to_delete
@@ -410,7 +411,6 @@ async def _calculate_sliding_sync_table_changes(
         if not to_insert and not to_delete:
             return SlidingSyncTableChanges(
                 room_id=room_id,
-                joined_room_best_effort_most_recent_stream_ordering=None,
                 joined_room_bump_stamp_to_fully_insert=None,
                 joined_room_updates={},
                 membership_snapshot_shared_insert_values={},
@@ -469,24 +469,24 @@ async def _calculate_sliding_sync_table_changes(
                 membership_event_id,
                 user_id,
             ) in membership_event_id_to_user_id_map.items():
-                # We should only be seeing events with `stream_ordering`/`instance_name` assigned by this point
-                membership_event_stream_ordering = membership_event_map[
-                    membership_event_id
-                ].internal_metadata.stream_ordering
-                assert membership_event_stream_ordering is not None
-                membership_event_instance_name = membership_event_map[
-                    membership_event_id
-                ].internal_metadata.instance_name
-                assert membership_event_instance_name is not None
-
                 membership_infos_to_insert_membership_snapshots.append(
+                    # XXX: We don't use `SlidingSyncMembershipInfoWithEventPos` here
+                    # because we're sourcing the event from `events_and_contexts`, we
+                    # can't rely on `stream_ordering`/`instance_name` being correct. We
+                    # could be working with events that were previously persisted as an
+                    # `outlier` with one `stream_ordering` but are now being persisted
+                    # again and de-outliered and assigned a different `stream_ordering`
+                    # that won't end up being used. Since we call
+                    # `_calculate_sliding_sync_table_changes()` before
+                    # `_update_outliers_txn()` which fixes this discrepancy (always use
+                    # the `stream_ordering` from the first time it was persisted), we're
+                    # working with an unreliable `stream_ordering` value that will
+                    # possibly be unused and not make it into the `events` table.
                     SlidingSyncMembershipInfo(
                         user_id=user_id,
                         sender=membership_event_map[membership_event_id].sender,
                         membership_event_id=membership_event_id,
                         membership=membership_event_map[membership_event_id].membership,
-                        membership_event_stream_ordering=membership_event_stream_ordering,
-                        membership_event_instance_name=membership_event_instance_name,
                     )
                 )
 
@@ -568,7 +568,6 @@ async def _calculate_sliding_sync_table_changes(
         # `_update_sliding_sync_tables_with_new_persisted_events_txn()`)
         #
         joined_room_updates: SlidingSyncStateInsertValues = {}
-        best_effort_most_recent_stream_ordering: Optional[int] = None
         bump_stamp_to_fully_insert: Optional[int] = None
         if not delta_state.no_longer_in_room:
             current_state_ids_map = {}
@@ -657,52 +656,9 @@ async def _calculate_sliding_sync_table_changes(
                 elif state_key == (EventTypes.Name, ""):
                     joined_room_updates["room_name"] = None
 
-            # Figure out `best_effort_most_recent_stream_ordering`. This doesn't need to
-            # be perfect, we just need *some* answer that points to a real event in the
-            # room in case we are the first ones inserting into the
-            # `sliding_sync_joined_rooms` table because of the `NON NULL` constraint on
-            # `event_stream_ordering`. In reality,
-            # `_update_sliding_sync_tables_with_new_persisted_events_txn()` is run after
-            # `_update_current_state_txn()` whenever a new event is persisted to update
-            # it to the correct latest value.
-            #
-            if len(events_and_contexts) > 0:
-                # Since the list is sorted ascending by `stream_ordering`, the last event
-                # should have the highest `stream_ordering`.
-                best_effort_most_recent_stream_ordering = events_and_contexts[-1][
-                    0
-                ].internal_metadata.stream_ordering
-            else:
-                # If there are no `events_and_contexts`, we assume it's one of two scenarios:
-                #  1. If there are new state `to_insert` but no `events_and_contexts`,
-                #     then it's a state reset.
-                #  2. Otherwise, it's some partial-state room re-syncing the current state and
-                #     going through un-partial process.
-                #
-                # Either way, we assume no new events are being persisted and we can
-                # find the latest already in the database. Since this is a best-effort
-                # value, we don't need to be perfect although I think we're pretty close
-                # here.
-                most_recent_event_pos_results = (
-                    await self.store.get_last_event_pos_in_room(
-                        room_id, event_types=None
-                    )
-                )
-                assert most_recent_event_pos_results, (
-                    f"We should not be seeing `None` here because we are still in the room ({room_id}) and "
-                    + "it should at-least have a join membership event that's keeping us here."
-                )
-                best_effort_most_recent_stream_ordering = most_recent_event_pos_results[
-                    1
-                ].stream
-
-            # We should have found a value if we are still in the room
-            assert best_effort_most_recent_stream_ordering is not None
-
         return SlidingSyncTableChanges(
             room_id=room_id,
             # For `sliding_sync_joined_rooms`
-            joined_room_best_effort_most_recent_stream_ordering=best_effort_most_recent_stream_ordering,
             joined_room_bump_stamp_to_fully_insert=bump_stamp_to_fully_insert,
             joined_room_updates=joined_room_updates,
             # For `sliding_sync_membership_snapshots`
@@ -1773,31 +1729,53 @@ def _update_current_state_txn(
             #
             # We only need to update when one of the relevant state values has changed
             if sliding_sync_table_changes.joined_room_updates:
-                # This should be *some* value that points to a real event in the room if
-                # we are still joined to the room.
-                assert (
-                    sliding_sync_table_changes.joined_room_best_effort_most_recent_stream_ordering
-                    is not None
+                sliding_sync_updates_keys = (
+                    sliding_sync_table_changes.joined_room_updates.keys()
+                )
+                sliding_sync_updates_values = (
+                    sliding_sync_table_changes.joined_room_updates.values()
                 )
 
-                self.db_pool.simple_upsert_txn(
-                    txn,
-                    table="sliding_sync_joined_rooms",
-                    keyvalues={"room_id": room_id},
-                    values=sliding_sync_table_changes.joined_room_updates,
-                    insertion_values={
-                        # The reason we're only *inserting* (not *updating*)
-                        # `event_stream_ordering` here is because the column has a `NON
-                        # NULL` constraint and we need *some* answer. And if the row
-                        # already exists, it already has the correct value and it's
-                        # better to just rely on
-                        # `_update_sliding_sync_tables_with_new_persisted_events_txn()`
-                        # to do the right thing (same for `bump_stamp`).
-                        "event_stream_ordering": sliding_sync_table_changes.joined_room_best_effort_most_recent_stream_ordering,
-                        # If we're trying to fully-insert a row, we need to provide a
-                        # value for `bump_stamp` if it exists for the room.
-                        "bump_stamp": sliding_sync_table_changes.joined_room_bump_stamp_to_fully_insert,
-                    },
+                args: List[Any] = [
+                    room_id,
+                    room_id,
+                    sliding_sync_table_changes.joined_room_bump_stamp_to_fully_insert,
+                ]
+                args.extend(iter(sliding_sync_updates_values))
+
+                # We use a sub-query for `stream_ordering` because it's unreliable to
+                # pre-calculate from `events_and_contexts` at the time when
+                # `_calculate_sliding_sync_table_changes()` is ran. We could be working
+                # with events that were previously persisted as an `outlier` with one
+                # `stream_ordering` but are now being persisted again and de-outliered
+                # and assigned a different `stream_ordering`. Since we call
+                # `_calculate_sliding_sync_table_changes()` before
+                # `_update_outliers_txn()` which fixes this discrepancy (always use the
+                # `stream_ordering` from the first time it was persisted), we're working
+                # with an unreliable `stream_ordering` value that will possibly be
+                # unused and not make it into the `events` table.
+                #
+                # We don't update `event_stream_ordering` `ON CONFLICT` because it's
+                # simpler and we can just rely on
+                # `_update_sliding_sync_tables_with_new_persisted_events_txn()` to do
+                # the right thing (same for `bump_stamp`). The only reason we're
+                # inserting `event_stream_ordering` here is because the column has a
+                # `NON NULL` constraint and we need some answer.
+                txn.execute(
+                    f"""
+                    INSERT INTO sliding_sync_joined_rooms
+                        (room_id, event_stream_ordering, bump_stamp, {", ".join(sliding_sync_updates_keys)})
+                    VALUES (
+                        ?,
+                        (SELECT stream_ordering FROM events WHERE room_id = ? ORDER BY stream_ordering DESC LIMIT 1),
+                        ?,
+                        {", ".join("?" for _ in sliding_sync_updates_values)}
+                    )
+                    ON CONFLICT (room_id)
+                    DO UPDATE SET
+                        {", ".join(f"{key} = EXCLUDED.{key}" for key in sliding_sync_updates_keys)}
+                    """,
+                    args,
                 )
 
         # We now update `local_current_membership`. We do this regardless
@@ -1854,38 +1832,63 @@ def _update_current_state_txn(
         if sliding_sync_table_changes.to_insert_membership_snapshots:
             # Update the `sliding_sync_membership_snapshots` table
             #
-            # We need to insert/update regardless of whether we have `sliding_sync_snapshot_keys`
-            # because there are other fields in the `ON CONFLICT` upsert to run (see
-            # inherit case above for more context when this happens).
-            self.db_pool.simple_upsert_many_txn(
-                txn=txn,
-                table="sliding_sync_membership_snapshots",
-                key_names=("room_id", "user_id"),
-                key_values=[
-                    (room_id, membership_info.user_id)
-                    for membership_info in sliding_sync_table_changes.to_insert_membership_snapshots
-                ],
-                value_names=[
-                    "sender",
-                    "membership_event_id",
-                    "membership",
-                    "event_stream_ordering",
-                    "event_instance_name",
-                ]
-                + list(
-                    sliding_sync_table_changes.membership_snapshot_shared_insert_values.keys()
-                ),
-                value_values=[
+            sliding_sync_snapshot_keys = (
+                sliding_sync_table_changes.membership_snapshot_shared_insert_values.keys()
+            )
+            sliding_sync_snapshot_values = (
+                sliding_sync_table_changes.membership_snapshot_shared_insert_values.values()
+            )
+            # We need to insert/update regardless of whether we have
+            # `sliding_sync_snapshot_keys` because there are other fields in the `ON
+            # CONFLICT` upsert to run (see inherit case (explained in
+            # `_calculate_sliding_sync_table_changes()`) for more context when this
+            # happens).
+            #
+            # XXX: We use a sub-query for `stream_ordering` because it's unreliable to
+            # pre-calculate from `events_and_contexts` at the time when
+            # `_calculate_sliding_sync_table_changes()` is ran. We could be working with
+            # events that were previously persisted as an `outlier` with one
+            # `stream_ordering` but are now being persisted again and de-outliered and
+            # assigned a different `stream_ordering` that won't end up being used. Since
+            # we call `_calculate_sliding_sync_table_changes()` before
+            # `_update_outliers_txn()` which fixes this discrepancy (always use the
+            # `stream_ordering` from the first time it was persisted), we're working
+            # with an unreliable `stream_ordering` value that will possibly be unused
+            # and not make it into the `events` table.
+            txn.execute_batch(
+                f"""
+                INSERT INTO sliding_sync_membership_snapshots
+                    (room_id, user_id, sender, membership_event_id, membership, event_stream_ordering, event_instance_name
+                    {("," + ", ".join(sliding_sync_snapshot_keys)) if sliding_sync_snapshot_keys else ""})
+                VALUES (
+                    ?, ?, ?, ?, ?,
+                    (SELECT stream_ordering FROM events WHERE event_id = ?),
+                    (SELECT instance_name FROM events WHERE event_id = ?)
+                    {("," + ", ".join("?" for _ in sliding_sync_snapshot_values)) if sliding_sync_snapshot_values else ""}
+                )
+                ON CONFLICT (room_id, user_id)
+                DO UPDATE SET
+                    sender = EXCLUDED.sender,
+                    membership_event_id = EXCLUDED.membership_event_id,
+                    membership = EXCLUDED.membership,
+                    event_stream_ordering = EXCLUDED.event_stream_ordering
+                    {("," + ", ".join(f"{key} = EXCLUDED.{key}" for key in sliding_sync_snapshot_keys)) if sliding_sync_snapshot_keys else ""}
+                """,
+                [
                     [
+                        room_id,
+                        membership_info.user_id,
                         membership_info.sender,
                         membership_info.membership_event_id,
                         membership_info.membership,
-                        membership_info.membership_event_stream_ordering,
-                        membership_info.membership_event_instance_name,
+                        # XXX: We do not use `membership_info.membership_event_stream_ordering` here
+                        # because it is an unreliable value. See XXX note above.
+                        membership_info.membership_event_id,
+                        # XXX: We do not use `membership_info.membership_event_instance_name` here
+                        # because it is an unreliable value. See XXX note above.
+                        membership_info.membership_event_id,
                     ]
-                    + list(
-                        sliding_sync_table_changes.membership_snapshot_shared_insert_values.values()
-                    )
+                    + list(sliding_sync_snapshot_values)
                     for membership_info in sliding_sync_table_changes.to_insert_membership_snapshots
                 ],
             )