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Fix background update for sliding sync (find previous membership) (v2) #17632

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Merged
erikjohnston merged 3 commits into from
Aug 29, 2024
Merged

Fix background update for sliding sync (find previous membership) (v2) #17632

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Fix background update for sliding sync (find previous membership)
erikjohnston Aug 29, 2024
3340f18
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erikjohnston Aug 29, 2024
e4f731b
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erikjohnston Aug 29, 2024
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1 change: 1 addition & 0 deletions changelog.d/17632.misc
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Original file line number Diff line number Diff line change
@@ -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.
9 changes: 5 additions & 4 deletions synapse/storage/databases/main/events_bg_updates.py
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Expand Up @@ -1967,12 +1967,13 @@ def _find_previous_membership_txn(
txn.execute(
"""
SELECT event_id, membership
FROM room_memberships
FROM room_memberships AS m
INNER JOIN events AS e USING (room_id, event_id)

@MadLittleMods MadLittleMods Aug 29, 2024

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Just double-checking that looking it up this way isn't slow vs just by (event_id)

The events table does have "events_room_stream" btree (room_id, stream_ordering) so I think this could work fast.

@erikjohnston erikjohnston Aug 29, 2024

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Yeah, empirically seems fast. Also helped by the fact these rooms should have very few events in them (generally just an invite then rejection)

WHERE
room_id = ?
AND user_id = ?
AND event_stream_ordering < ?
ORDER BY event_stream_ordering DESC
AND m.user_id = ?
AND e.stream_ordering < ?
ORDER BY e.stream_ordering DESC

@MadLittleMods MadLittleMods Aug 29, 2024 •
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For onlookers, see context in #17631 (comment)

LIMIT 1
""",
(
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