Fix a potentially-huge sql query (#7274)
We could end up looking up tens of thousands of events, which could cause large amounts of data to be logged to the postgres log.
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Fix a sql query introduced in Synapse 1.12.0 which could cause large amounts of logging to the postgres slow-query log.
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@ -173,19 +173,28 @@ class EventFederationWorkerStore(EventsWorkerStore, SignatureWorkerStore, SQLBas
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for event_id in initial_events
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}
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# The sorted list of events whose auth chains we should walk.
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search = [] # type: List[Tuple[int, str]]
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# We need to get the depth of the initial events for sorting purposes.
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sql = """
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SELECT depth, event_id FROM events
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WHERE %s
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ORDER BY depth ASC
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"""
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# the list can be huge, so let's avoid looking them all up in one massive
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# query.
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for batch in batch_iter(initial_events, 1000):
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clause, args = make_in_list_sql_clause(
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txn.database_engine, "event_id", initial_events
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txn.database_engine, "event_id", batch
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)
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txn.execute(sql % (clause,), args)
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# The sorted list of events whose auth chains we should walk.
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search = txn.fetchall() # type: List[Tuple[int, str]]
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# I think building a temporary list with fetchall is more efficient than
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# just `search.extend(txn)`, but this is unconfirmed
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search.extend(txn.fetchall())
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# sort by depth
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search.sort()
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# Map from event to its auth events
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event_to_auth_events = {} # type: Dict[str, Set[str]]
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