diff --git a/changelog.d/13353.bugfix b/changelog.d/13353.bugfix
new file mode 100644
index 0000000000..8e18bfae1f
--- /dev/null
+++ b/changelog.d/13353.bugfix
@@ -0,0 +1 @@
+Fix a bug in the experimental faster-room-joins support which could cause it to get stuck in an infinite loop.
diff --git a/synapse/handlers/federation_event.py b/synapse/handlers/federation_event.py
index fc1254d2ad..2ba2b1527e 100644
--- a/synapse/handlers/federation_event.py
+++ b/synapse/handlers/federation_event.py
@@ -569,15 +569,15 @@ class FederationEventHandler:
if context is None or context.partial_state:
# this can happen if some or all of the event's prev_events still have
- # partial state - ie, an event has an earlier stream_ordering than one
- # or more of its prev_events, so we de-partial-state it before its
- # prev_events.
+ # partial state. We were careful to only pick events from the db without
+ # partial-state prev events, so that implies that a prev event has
+ # been persisted (with partial state) since we did the query.
#
- # TODO(faster_joins): we probably need to be more intelligent, and
- # exclude partial-state prev_events from consideration
- # https://github.com/matrix-org/synapse/issues/13001
+ # So, let's just ignore `event` for now; when we re-run the db query
+ # we should instead get its partial-state prev event, which we will
+ # de-partial-state, and then come back to event.
logger.warning(
- "%s still has partial state: can't de-partial-state it yet",
+ "%s still has prev_events with partial state: can't de-partial-state it yet",
event.event_id,
)
return
diff --git a/synapse/storage/databases/main/events_worker.py b/synapse/storage/databases/main/events_worker.py
index 5914a35420..29c99c6357 100644
--- a/synapse/storage/databases/main/events_worker.py
+++ b/synapse/storage/databases/main/events_worker.py
@@ -2110,11 +2110,29 @@ class EventsWorkerStore(SQLBaseStore):
def _get_partial_state_events_batch_txn(
txn: LoggingTransaction, room_id: str
) -> List[str]:
+ # we want to work through the events from oldest to newest, so
+ # we only want events whose prev_events do *not* have partial state - hence
+ # the 'NOT EXISTS' clause in the below.
+ #
+ # This is necessary because ordering by stream ordering isn't quite enough
+ # to ensure that we work from oldest to newest event (in particular,
+ # if an event is initially persisted as an outlier and later de-outliered,
+ # it can end up with a lower stream_ordering than its prev_events).
+ #
+ # Typically this means we'll only return one event per batch, but that's
+ # hard to do much about.
+ #
+ # See also: https://github.com/matrix-org/synapse/issues/13001
txn.execute(
"""
SELECT event_id FROM partial_state_events AS pse
JOIN events USING (event_id)
- WHERE pse.room_id = ?
+ WHERE pse.room_id = ? AND
+ NOT EXISTS(
+ SELECT 1 FROM event_edges AS ee
+ JOIN partial_state_events AS prev_pse ON (prev_pse.event_id=ee.prev_event_id)
+ WHERE ee.event_id=pse.event_id
+ )
ORDER BY events.stream_ordering
LIMIT 100
""",
|
