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Commit521fd47

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Use weaker locks when updating pg_subscription_rel
The previously used ShareRowExclusiveLock, while technically probablymore correct, led to deadlocks during seemingly unrelated operations andthus a poor experience. Use RowExclusiveLock, like for most similarcatalog operations. In some care cases, the user might see an errorfrom DDL commands.Discussion:https://www.postgresql.org/message-id/flat/13592.1490851519%40sss.pgh.pa.usAuthor: Petr Jelinek <petr.jelinek@2ndquadrant.com>
1 parentc45b1d2 commit521fd47

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‎src/backend/catalog/pg_subscription.c

Lines changed: 7 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -214,6 +214,10 @@ textarray_to_stringlist(ArrayType *textarray)
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/*
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* Set the state of a subscription table.
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*
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* The insert-or-update logic in this function is not concurrency safe so it
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* might raise an error in rare circumstances. But if we took a stronger lock
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* such as ShareRowExclusiveLock, we would risk more deadlocks.
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*/
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Oid
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SetSubscriptionRelState(Oidsubid,Oidrelid,charstate,
@@ -225,8 +229,7 @@ SetSubscriptionRelState(Oid subid, Oid relid, char state,
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boolnulls[Natts_pg_subscription_rel];
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Datumvalues[Natts_pg_subscription_rel];
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228-
/* Prevent concurrent changes. */
229-
rel=heap_open(SubscriptionRelRelationId,ShareRowExclusiveLock);
232+
rel=heap_open(SubscriptionRelRelationId,RowExclusiveLock);
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/* Try finding existing mapping. */
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tup=SearchSysCacheCopy2(SUBSCRIPTIONRELMAP,
@@ -357,8 +360,7 @@ RemoveSubscriptionRel(Oid subid, Oid relid)
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HeapTupletup;
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intnkeys=0;
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360-
/* Prevent concurrent changes (see SetSubscriptionRelState()). */
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rel=heap_open(SubscriptionRelRelationId,ShareRowExclusiveLock);
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rel=heap_open(SubscriptionRelRelationId,RowExclusiveLock);
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if (OidIsValid(subid))
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{
@@ -386,7 +388,7 @@ RemoveSubscriptionRel(Oid subid, Oid relid)
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}
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heap_endscan(scan);
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389-
heap_close(rel,ShareRowExclusiveLock);
391+
heap_close(rel,RowExclusiveLock);
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}
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