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Fix data loss at inplace update after heap_update().

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As previously-added tests demonstrated, heap_inplace_update() could
instead update an unrelated tuple of the same catalog.  It could lose
the update.  Losing relhasindex=t was a source of index corruption.
Inplace-updating commands like VACUUM will now wait for heap_update()
commands like GRANT TABLE and GRANT DATABASE.  That isn't ideal, but a
long-running GRANT already hurts VACUUM progress more just by keeping an
XID running.  The VACUUM will behave like a DELETE or UPDATE waiting for
the uncommitted change.

For implementation details, start at the systable_inplace_update_begin()
header comment and README.tuplock.  Back-patch to v12 (all supported
versions).  In back branches, retain a deprecated heap_inplace_update(),
for extensions.

Reported by Smolkin Grigory.  Reviewed by Nitin Motiani, (in earlier
versions) Heikki Linnakangas, and (in earlier versions) Alexander
Lakhin.

Discussion: https://postgr.es/m/CAMp+ueZQz3yDk7qg42hk6-9gxniYbp-=bG2mgqecErqR5gGGOA@mail.gmail.com
This commit is contained in:
Noah Misch
2024-09-24 15:25:18 -07:00
parent dbf3f974ee
commit a07e03fd8f
16 changed files with 801 additions and 155 deletions
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27
src/backend/commands/event_trigger.c
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@@ -946,25 +946,18 @@ EventTriggerOnLogin(void)
{
Relation pg_db = table_open(DatabaseRelationId, RowExclusiveLock);
HeapTuple tuple;
void *state;
Form_pg_database db;
ScanKeyData key[1];
SysScanDesc scan;
/*
* Get the pg_database tuple to scribble on. Note that this does
* not directly rely on the syscache to avoid issues with
* flattened toast values for the in-place update.
*/
/* Fetch a copy of the tuple to scribble on */
ScanKeyInit(&key[0],
Anum_pg_database_oid,
BTEqualStrategyNumber, F_OIDEQ,
ObjectIdGetDatum(MyDatabaseId));
scan = systable_beginscan(pg_db, DatabaseOidIndexId, true,
NULL, 1, key);
tuple = systable_getnext(scan);
tuple = heap_copytuple(tuple);
systable_endscan(scan);
systable_inplace_update_begin(pg_db, DatabaseOidIndexId, true,
NULL, 1, key, &tuple, &state);
if (!HeapTupleIsValid(tuple))
elog(ERROR, "could not find tuple for database %u", MyDatabaseId);
@@ -980,13 +973,15 @@ EventTriggerOnLogin(void)
* that avoids possible waiting on the row-level lock. Second,
* that avoids dealing with TOAST.
*
* It's known that changes made by heap_inplace_update() may
* be lost due to concurrent normal updates. However, we are
* OK with that. The subsequent connections will still have a
* chance to set "dathasloginevt" to false.
* Changes made by inplace update may be lost due to
* concurrent normal updates; see inplace-inval.spec. However,
* we are OK with that. The subsequent connections will still
* have a chance to set "dathasloginevt" to false.
*/
heap_inplace_update(pg_db, tuple);
systable_inplace_update_finish(state, tuple);
}
else
systable_inplace_update_cancel(state);
table_close(pg_db, RowExclusiveLock);
heap_freetuple(tuple);
}