get_constraint_index(Oid constraintId)
{
	Oid			indexId = InvalidOid;
	Relation	depRel;
	ScanKeyData key[3];
	SysScanDesc scan;
	HeapTuple	tup;

	/* Search the dependency table for the dependent index */
	depRel = heap_open(DependRelationId, AccessShareLock);

	ScanKeyInit(&key[0],
				Anum_pg_depend_refclassid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(ConstraintRelationId));
	ScanKeyInit(&key[1],
				Anum_pg_depend_refobjid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(constraintId));
	ScanKeyInit(&key[2],
				Anum_pg_depend_refobjsubid,
				BTEqualStrategyNumber, F_INT4EQ,
				Int32GetDatum(0));

	scan = systable_beginscan(depRel, DependReferenceIndexId, true,
							  NULL, 3, key);

	while (HeapTupleIsValid(tup = systable_getnext(scan)))
	{
		Form_pg_depend deprec = (Form_pg_depend) GETSTRUCT(tup);

		/*
		 * We assume any internal dependency of an index on the constraint
		 * must be what we are looking for.  (The relkind test is just
		 * paranoia; there shouldn't be any such dependencies otherwise.)
		 */
		if (deprec->classid == RelationRelationId &&
			deprec->objsubid == 0 &&
			deprec->deptype == DEPENDENCY_INTERNAL &&
			get_rel_relkind(deprec->objid) == RELKIND_INDEX)
		{
			indexId = deprec->objid;
			break;
		}
	}

	systable_endscan(scan);
	heap_close(depRel, AccessShareLock);

	return indexId;
}
get_constraint_index(Oid constraintId)
{
	Oid			indexId = InvalidOid;
	Relation	depRel;
	ScanKeyData key[3];
	SysScanDesc scan;
	HeapTuple	tup;

	 
	depRel = heap_open(DependRelationId, AccessShareLock);

	ScanKeyInit(&key[0],
				Anum_pg_depend_refclassid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(ConstraintRelationId));
	ScanKeyInit(&key[1],
				Anum_pg_depend_refobjid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(constraintId));
	ScanKeyInit(&key[2],
				Anum_pg_depend_refobjsubid,
				BTEqualStrategyNumber, F_INT4EQ,
				Int32GetDatum(0));

	scan = systable_beginscan(depRel, DependReferenceIndexId, true,
							  NULL, 3, key);

	while (HeapTupleIsValid(tup = systable_getnext(scan)))
	{
		Form_pg_depend deprec = (Form_pg_depend) GETSTRUCT(tup);

		 
		if (deprec->classid == RelationRelationId &&
			deprec->objsubid == 0 &&
			deprec->deptype == DEPENDENCY_INTERNAL &&
			get_rel_relkind(deprec->objid) == RELKIND_INDEX)
		{
			indexId = deprec->objid;
			break;
		}
	}

	systable_endscan(scan);
	heap_close(depRel, AccessShareLock);

	return indexId;
}