Fix unsafe memory management in CloneRowTriggersToPartition().
It's not really supported to call systable_getnext() in a different memory context than systable_beginscan() was called in, and it's *definitely* not safe to do so and then reset that context between calls. I'm not very clear on how this code survived CLOBBER_CACHE_ALWAYS testing ... but Alexander Lakhin found a case that would crash it pretty reliably. Per bug #15828. Fix, and backpatch to v11 where this code came in. Discussion: https://postgr.es/m/15828-f6ddd7df4852f473@postgresql.org
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@ -15772,8 +15772,7 @@ CloneRowTriggersToPartition(Relation parent, Relation partition)
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ScanKeyData key;
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SysScanDesc scan;
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HeapTuple tuple;
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MemoryContext oldcxt,
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perTupCxt;
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MemoryContext perTupCxt;
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ScanKeyInit(&key, Anum_pg_trigger_tgrelid, BTEqualStrategyNumber,
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F_OIDEQ, ObjectIdGetDatum(RelationGetRelid(parent)));
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@ -15783,18 +15782,16 @@ CloneRowTriggersToPartition(Relation parent, Relation partition)
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perTupCxt = AllocSetContextCreate(CurrentMemoryContext,
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"clone trig", ALLOCSET_SMALL_SIZES);
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oldcxt = MemoryContextSwitchTo(perTupCxt);
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while (HeapTupleIsValid(tuple = systable_getnext(scan)))
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{
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Form_pg_trigger trigForm;
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Form_pg_trigger trigForm = (Form_pg_trigger) GETSTRUCT(tuple);
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CreateTrigStmt *trigStmt;
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Node *qual = NULL;
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Datum value;
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bool isnull;
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List *cols = NIL;
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trigForm = (Form_pg_trigger) GETSTRUCT(tuple);
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MemoryContext oldcxt;
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/*
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* Ignore statement-level triggers; those are not cloned.
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@ -15813,6 +15810,9 @@ CloneRowTriggersToPartition(Relation parent, Relation partition)
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elog(ERROR, "unexpected trigger \"%s\" found",
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NameStr(trigForm->tgname));
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/* Use short-lived context for CREATE TRIGGER */
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oldcxt = MemoryContextSwitchTo(perTupCxt);
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/*
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* If there is a WHEN clause, generate a 'cooked' version of it that's
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* appropriate for the partition.
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@ -15876,10 +15876,10 @@ CloneRowTriggersToPartition(Relation parent, Relation partition)
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trigForm->tgfoid, trigForm->oid, qual,
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false, true);
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MemoryContextSwitchTo(oldcxt);
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MemoryContextReset(perTupCxt);
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}
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MemoryContextSwitchTo(oldcxt);
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MemoryContextDelete(perTupCxt);
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systable_endscan(scan);
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