Function ATDetachCheckNoForeignKeyRefs

src/backend/commands/tablecmds.c:23079–23124

* During DETACH PARTITION, verify that any foreign keys pointing to the * partitioned table would not become invalid. An error is raised if any * referenced values exist. */

 * referenced values exist.
 */
static void
ATDetachCheckNoForeignKeyRefs(Relation partition)
{
	List	   *constraints;
	ListCell   *cell;

	constraints = GetParentedForeignKeyRefs(partition);

	foreach(cell, constraints)
	{
		Oid			constrOid = lfirst_oid(cell);
		HeapTuple	tuple;
		Form_pg_constraint constrForm;
		Relation	rel;
		Trigger		trig;

		tuple = SearchSysCache1(CONSTROID, ObjectIdGetDatum(constrOid));
		if (!HeapTupleIsValid(tuple))
			elog(ERROR, "cache lookup failed for constraint %u", constrOid);
		constrForm = (Form_pg_constraint) GETSTRUCT(tuple);

		Assert(OidIsValid(constrForm->conparentid));
		Assert(constrForm->confrelid == RelationGetRelid(partition));

		/* prevent data changes into the referencing table until commit */
		rel = table_open(constrForm->conrelid, ShareLock);

		MemSet(&trig, 0, sizeof(trig));
		trig.tgoid = InvalidOid;
		trig.tgname = NameStr(constrForm->conname);
		trig.tgenabled = TRIGGER_FIRES_ON_ORIGIN;
		trig.tgisinternal = true;
		trig.tgconstrrelid = RelationGetRelid(partition);
		trig.tgconstrindid = constrForm->conindid;
		trig.tgconstraint = constrForm->oid;
		trig.tgdeferrable = false;
		trig.tginitdeferred = false;
		/* we needn't fill in remaining fields */

		RI_PartitionRemove_Check(&trig, rel, partition);

		ReleaseSysCache(tuple);

		table_close(rel, NoLock);
	}
}

/*
 * resolve column compression specification to compression method.