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Fix creation of duplicate foreign keys on partitions

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When creating a foreign key in a partitioned table, if some partitions
already have equivalent constraints, we wastefully create duplicates of
the constraints instead of attaching to the existing ones.  That's
inconsistent with the de-duplication that is applied when a table is
attached as a partition.  To fix, reuse the FK-cloning code instead of
having a separate code path.

Backpatch to Postgres 11.  This is a subtle behavior change, but surely
a welcome one since there's no use in having duplicate foreign keys.

Discovered by Álvaro Herrera while thinking about a different problem
reported by Jesper Pedersen (bug #15587).

Author: Álvaro Herrera
Discussion: https://postgr.es/m/201901151935.zfadrzvyof4k@alvherre.pgsql
This commit is contained in:
Alvaro Herrera
2019-01-18 14:49:40 -03:00
parent 03afae201f
commit 0325d7a595
3 changed files with 152 additions and 12 deletions
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43
src/backend/commands/tablecmds.c
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@ -7658,31 +7658,50 @@ ATAddForeignKeyConstraint(List **wqueue, AlteredTableInfo *tab, Relation rel,
if (recurse && rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
{
PartitionDesc partdesc;
Relation pg_constraint;
List *cloned = NIL;
ListCell *cell;
pg_constraint = heap_open(ConstraintRelationId, RowExclusiveLock);
partdesc = RelationGetPartitionDesc(rel);
for (i = 0; i < partdesc->nparts; i++)
{
Oid partitionId = partdesc->oids[i];
Relation partition = heap_open(partitionId, lockmode);
AlteredTableInfo *childtab;
ObjectAddress childAddr;
CheckTableNotInUse(partition, "ALTER TABLE");
/* Find or create work queue entry for this table */
childtab = ATGetQueueEntry(wqueue, partition);
childAddr =
ATAddForeignKeyConstraint(wqueue, childtab, partition,
fkconstraint, constrOid,
recurse, true, lockmode);
/* Record this constraint as dependent on the parent one */
recordDependencyOn(&childAddr, &address, DEPENDENCY_INTERNAL_AUTO);
CloneFkReferencing(pg_constraint, rel, partition,
list_make1_oid(constrOid),
&cloned);
heap_close(partition, NoLock);
}
heap_close(pg_constraint, RowExclusiveLock);
foreach(cell, cloned)
{
ClonedConstraint *cc = (ClonedConstraint *) lfirst(cell);
Relation partition = heap_open(cc->relid, lockmode);
AlteredTableInfo *childtab;
NewConstraint *newcon;
/* Find or create work queue entry for this partition */
childtab = ATGetQueueEntry(wqueue, partition);
newcon = (NewConstraint *) palloc0(sizeof(NewConstraint));
newcon->name = cc->constraint->conname;
newcon->contype = CONSTR_FOREIGN;
newcon->refrelid = cc->refrelid;
newcon->refindid = cc->conindid;
newcon->conid = cc->conid;
newcon->qual = (Node *) fkconstraint;
childtab->constraints = lappend(childtab->constraints, newcon);
heap_close(partition, lockmode);
}
}
/*