Attempt to delete more duplicate rows in receipts_linearized table. (#14915)

The previous assumption was that the stream_id column was unique
(for a room ID, receipt type, user ID tuple), but this turned out to be
incorrect.

Now find the max stream ID, then map this back to a database-specific
row identifier and delete other rows which match the (room ID, receipt type,
user ID) tuple, but *not* the row ID.
This commit is contained in:
Patrick Cloke 2023-02-01 15:45:10 -05:00 committed by GitHub
parent bb675913f0
commit 230a831c73
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3 changed files with 30 additions and 9 deletions

1
changelog.d/14915.bugfix Normal file
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@ -0,0 +1 @@
Fix a bug introduced in Synapse 1.70.0 where the background updates to add non-thread unique indexes on receipts could fail when upgrading from 1.67.0 or earlier.

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@ -941,10 +941,14 @@ class ReceiptsBackgroundUpdateStore(SQLBaseStore):
receipts."""
def _remote_duplicate_receipts_txn(txn: LoggingTransaction) -> None:
if isinstance(self.database_engine, PostgresEngine):
ROW_ID_NAME = "ctid"
else:
ROW_ID_NAME = "rowid"
# Identify any duplicate receipts arising from
# https://github.com/matrix-org/synapse/issues/14406.
# We expect the following query to use the per-thread receipt index and take
# less than a minute.
# The following query takes less than a minute on matrix.org.
sql = """
SELECT MAX(stream_id), room_id, receipt_type, user_id
FROM receipts_linearized
@ -956,19 +960,33 @@ class ReceiptsBackgroundUpdateStore(SQLBaseStore):
duplicate_keys = cast(List[Tuple[int, str, str, str]], list(txn))
# Then remove duplicate receipts, keeping the one with the highest
# `stream_id`. There should only be a single receipt with any given
# `stream_id`.
for max_stream_id, room_id, receipt_type, user_id in duplicate_keys:
sql = """
# `stream_id`. Since there might be duplicate rows with the same
# `stream_id`, we delete by the ctid instead.
for stream_id, room_id, receipt_type, user_id in duplicate_keys:
sql = f"""
SELECT {ROW_ID_NAME}
FROM receipts_linearized
WHERE
room_id = ? AND
receipt_type = ? AND
user_id = ? AND
thread_id IS NULL AND
stream_id = ?
LIMIT 1
"""
txn.execute(sql, (room_id, receipt_type, user_id, stream_id))
row_id = cast(Tuple[str], txn.fetchone())[0]
sql = f"""
DELETE FROM receipts_linearized
WHERE
room_id = ? AND
receipt_type = ? AND
user_id = ? AND
thread_id IS NULL AND
stream_id < ?
{ROW_ID_NAME} != ?
"""
txn.execute(sql, (room_id, receipt_type, user_id, max_stream_id))
txn.execute(sql, (room_id, receipt_type, user_id, row_id))
await self.db_pool.runInteraction(
self.RECEIPTS_LINEARIZED_UNIQUE_INDEX_UPDATE_NAME,

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@ -168,7 +168,9 @@ class ReceiptsBackgroundUpdateStoreTestCase(HomeserverTestCase):
{"stream_id": 6, "event_id": "$some_event"},
],
(self.other_room_id, "m.read", self.user_id): [
{"stream_id": 7, "event_id": "$some_event"}
# It is possible for stream IDs to be duplicated.
{"stream_id": 7, "event_id": "$some_event"},
{"stream_id": 7, "event_id": "$some_event"},
],
},
expected_unique_receipts={