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In _purge_history_txn, ensure that txn.fetchall has elements before accessing rows (#10690)

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This change adds a check for row existence before accessing row element, this should fix issue #10669
Signed-off-by: Vasya Boytsov vasiliy.boytsov@phystech.edu
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Kokokokoka 2021-09-24 12:19:51 +03:00 committed by GitHub
parent 90d9fc7505
commit e704cc2a48
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2 changed files with 13 additions and 8 deletions
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changelog.d/10690.bugfix Normal file
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@ -0,0 +1 @@
Fix a long-standing bug that caused an `AssertionError` when purging history in certain rooms. Contributed by @Kokokokoka.

20
synapse/storage/databases/main/purge_events.py
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@ -102,15 +102,19 @@ class PurgeEventsStore(StateGroupWorkerStore, CacheInvalidationWorkerStore):
(room_id,),
)
rows = txn.fetchall()
max_depth = max(row[1] for row in rows)
# if we already have no forwards extremities (for example because they were
# cleared out by the `delete_old_current_state_events` background database
# update), then we may as well carry on.
if rows:
max_depth = max(row[1] for row in rows)
if max_depth < token.topological:
# We need to ensure we don't delete all the events from the database
# otherwise we wouldn't be able to send any events (due to not
# having any backwards extremities)
raise SynapseError(
400, "topological_ordering is greater than forward extremeties"
)
if max_depth < token.topological:
# We need to ensure we don't delete all the events from the database
# otherwise we wouldn't be able to send any events (due to not
# having any backwards extremities)
raise SynapseError(
400, "topological_ordering is greater than forward extremities"
)
logger.info("[purge] looking for events to delete")