diff --git a/src/backend/catalog/pg_constraint.c b/src/backend/catalog/pg_constraint.c
index 7a6d158..3d65464 100644
*** a/src/backend/catalog/pg_constraint.c
--- b/src/backend/catalog/pg_constraint.c
*************** CloneForeignKeyConstraints(Oid parentId,
*** 443,449 ****
  	ScanKeyInit(&key,
  				Anum_pg_constraint_conrelid, BTEqualStrategyNumber,
  				F_OIDEQ, ObjectIdGetDatum(parentId));
! 	scan = systable_beginscan(pg_constraint, ConstraintRelidIndexId, true,
  							  NULL, 1, &key);
  
  	while ((tuple = systable_getnext(scan)) != NULL)
--- 443,449 ----
  	ScanKeyInit(&key,
  				Anum_pg_constraint_conrelid, BTEqualStrategyNumber,
  				F_OIDEQ, ObjectIdGetDatum(parentId));
! 	scan = systable_beginscan(pg_constraint, ConstraintRelidTypidNameIndexId, true,
  							  NULL, 1, &key);
  
  	while ((tuple = systable_getnext(scan)) != NULL)
*************** AlterConstraintNamespaces(Oid ownerId, O
*** 944,975 ****
  						  Oid newNspId, bool isType, ObjectAddresses *objsMoved)
  {
  	Relation	conRel;
! 	ScanKeyData key[1];
  	SysScanDesc scan;
  	HeapTuple	tup;
  
  	conRel = heap_open(ConstraintRelationId, RowExclusiveLock);
  
! 	if (isType)
! 	{
! 		ScanKeyInit(&key[0],
! 					Anum_pg_constraint_contypid,
! 					BTEqualStrategyNumber, F_OIDEQ,
! 					ObjectIdGetDatum(ownerId));
! 
! 		scan = systable_beginscan(conRel, ConstraintTypidIndexId, true,
! 								  NULL, 1, key);
! 	}
! 	else
! 	{
! 		ScanKeyInit(&key[0],
! 					Anum_pg_constraint_conrelid,
! 					BTEqualStrategyNumber, F_OIDEQ,
! 					ObjectIdGetDatum(ownerId));
  
! 		scan = systable_beginscan(conRel, ConstraintRelidIndexId, true,
! 								  NULL, 1, key);
! 	}
  
  	while (HeapTupleIsValid((tup = systable_getnext(scan))))
  	{
--- 944,966 ----
  						  Oid newNspId, bool isType, ObjectAddresses *objsMoved)
  {
  	Relation	conRel;
! 	ScanKeyData key[2];
  	SysScanDesc scan;
  	HeapTuple	tup;
  
  	conRel = heap_open(ConstraintRelationId, RowExclusiveLock);
  
! 	ScanKeyInit(&key[0],
! 				Anum_pg_constraint_conrelid,
! 				BTEqualStrategyNumber, F_OIDEQ,
! 				ObjectIdGetDatum(isType ? InvalidOid : ownerId));
! 	ScanKeyInit(&key[1],
! 				Anum_pg_constraint_contypid,
! 				BTEqualStrategyNumber, F_OIDEQ,
! 				ObjectIdGetDatum(isType ? ownerId : InvalidOid));
  
! 	scan = systable_beginscan(conRel, ConstraintRelidTypidNameIndexId, true,
! 							  NULL, 2, key);
  
  	while (HeapTupleIsValid((tup = systable_getnext(scan))))
  	{
*************** get_relation_constraint_oid(Oid relid, c
*** 1059,1095 ****
  	Relation	pg_constraint;
  	HeapTuple	tuple;
  	SysScanDesc scan;
! 	ScanKeyData skey[1];
  	Oid			conOid = InvalidOid;
  
- 	/*
- 	 * Fetch the constraint tuple from pg_constraint.  There may be more than
- 	 * one match, because constraints are not required to have unique names;
- 	 * if so, error out.
- 	 */
  	pg_constraint = heap_open(ConstraintRelationId, AccessShareLock);
  
  	ScanKeyInit(&skey[0],
  				Anum_pg_constraint_conrelid,
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(relid));
  
! 	scan = systable_beginscan(pg_constraint, ConstraintRelidIndexId, true,
! 							  NULL, 1, skey);
  
! 	while (HeapTupleIsValid(tuple = systable_getnext(scan)))
  	{
! 		Form_pg_constraint con = (Form_pg_constraint) GETSTRUCT(tuple);
! 
! 		if (strcmp(NameStr(con->conname), conname) == 0)
! 		{
! 			if (OidIsValid(conOid))
! 				ereport(ERROR,
! 						(errcode(ERRCODE_DUPLICATE_OBJECT),
! 						 errmsg("table \"%s\" has multiple constraints named \"%s\"",
! 								get_rel_name(relid), conname)));
! 			conOid = HeapTupleGetOid(tuple);
! 		}
  	}
  
  	systable_endscan(scan);
--- 1050,1080 ----
  	Relation	pg_constraint;
  	HeapTuple	tuple;
  	SysScanDesc scan;
! 	ScanKeyData skey[3];
  	Oid			conOid = InvalidOid;
  
  	pg_constraint = heap_open(ConstraintRelationId, AccessShareLock);
  
  	ScanKeyInit(&skey[0],
  				Anum_pg_constraint_conrelid,
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(relid));
+ 	ScanKeyInit(&skey[1],
+ 				Anum_pg_constraint_contypid,
+ 				BTEqualStrategyNumber, F_OIDEQ,
+ 				ObjectIdGetDatum(InvalidOid));
+ 	ScanKeyInit(&skey[2],
+ 				Anum_pg_constraint_conname,
+ 				BTEqualStrategyNumber, F_NAMEEQ,
+ 				CStringGetDatum(conname));
  
! 	scan = systable_beginscan(pg_constraint, ConstraintRelidTypidNameIndexId, true,
! 							  NULL, 3, skey);
  
! 	/* There can be at most one matching row */
! 	if (HeapTupleIsValid(tuple = systable_getnext(scan)))
  	{
! 		conOid = HeapTupleGetOid(tuple);
  	}
  
  	systable_endscan(scan);
*************** get_relation_constraint_attnos(Oid relid
*** 1126,1192 ****
  	Relation	pg_constraint;
  	HeapTuple	tuple;
  	SysScanDesc scan;
! 	ScanKeyData skey[1];
  
  	/* Set *constraintOid, to avoid complaints about uninitialized vars */
  	*constraintOid = InvalidOid;
  
- 	/*
- 	 * Fetch the constraint tuple from pg_constraint.  There may be more than
- 	 * one match, because constraints are not required to have unique names;
- 	 * if so, error out.
- 	 */
  	pg_constraint = heap_open(ConstraintRelationId, AccessShareLock);
  
  	ScanKeyInit(&skey[0],
  				Anum_pg_constraint_conrelid,
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(relid));
  
! 	scan = systable_beginscan(pg_constraint, ConstraintRelidIndexId, true,
! 							  NULL, 1, skey);
  
! 	while (HeapTupleIsValid(tuple = systable_getnext(scan)))
  	{
- 		Form_pg_constraint con = (Form_pg_constraint) GETSTRUCT(tuple);
  		Datum		adatum;
  		bool		isNull;
- 		ArrayType  *arr;
- 		int16	   *attnums;
- 		int			numcols;
- 		int			i;
- 
- 		/* Check the constraint name */
- 		if (strcmp(NameStr(con->conname), conname) != 0)
- 			continue;
- 		if (OidIsValid(*constraintOid))
- 			ereport(ERROR,
- 					(errcode(ERRCODE_DUPLICATE_OBJECT),
- 					 errmsg("table \"%s\" has multiple constraints named \"%s\"",
- 							get_rel_name(relid), conname)));
  
  		*constraintOid = HeapTupleGetOid(tuple);
  
  		/* Extract the conkey array, ie, attnums of constrained columns */
  		adatum = heap_getattr(tuple, Anum_pg_constraint_conkey,
  							  RelationGetDescr(pg_constraint), &isNull);
! 		if (isNull)
! 			continue;			/* no constrained columns */
  
! 		arr = DatumGetArrayTypeP(adatum);	/* ensure not toasted */
! 		numcols = ARR_DIMS(arr)[0];
! 		if (ARR_NDIM(arr) != 1 ||
! 			numcols < 0 ||
! 			ARR_HASNULL(arr) ||
! 			ARR_ELEMTYPE(arr) != INT2OID)
! 			elog(ERROR, "conkey is not a 1-D smallint array");
! 		attnums = (int16 *) ARR_DATA_PTR(arr);
  
! 		/* Construct the result value */
! 		for (i = 0; i < numcols; i++)
! 		{
! 			conattnos = bms_add_member(conattnos,
! 									   attnums[i] - FirstLowInvalidHeapAttributeNumber);
  		}
  	}
  
--- 1111,1172 ----
  	Relation	pg_constraint;
  	HeapTuple	tuple;
  	SysScanDesc scan;
! 	ScanKeyData skey[3];
  
  	/* Set *constraintOid, to avoid complaints about uninitialized vars */
  	*constraintOid = InvalidOid;
  
  	pg_constraint = heap_open(ConstraintRelationId, AccessShareLock);
  
  	ScanKeyInit(&skey[0],
  				Anum_pg_constraint_conrelid,
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(relid));
+ 	ScanKeyInit(&skey[1],
+ 				Anum_pg_constraint_contypid,
+ 				BTEqualStrategyNumber, F_OIDEQ,
+ 				ObjectIdGetDatum(InvalidOid));
+ 	ScanKeyInit(&skey[2],
+ 				Anum_pg_constraint_conname,
+ 				BTEqualStrategyNumber, F_NAMEEQ,
+ 				CStringGetDatum(conname));
  
! 	scan = systable_beginscan(pg_constraint, ConstraintRelidTypidNameIndexId, true,
! 							  NULL, 3, skey);
  
! 	/* There can be at most one matching row */
! 	if (HeapTupleIsValid(tuple = systable_getnext(scan)))
  	{
  		Datum		adatum;
  		bool		isNull;
  
  		*constraintOid = HeapTupleGetOid(tuple);
  
  		/* Extract the conkey array, ie, attnums of constrained columns */
  		adatum = heap_getattr(tuple, Anum_pg_constraint_conkey,
  							  RelationGetDescr(pg_constraint), &isNull);
! 		if (!isNull)
! 		{
! 			ArrayType  *arr;
! 			int			numcols;
! 			int16	   *attnums;
! 			int			i;
  
! 			arr = DatumGetArrayTypeP(adatum);	/* ensure not toasted */
! 			numcols = ARR_DIMS(arr)[0];
! 			if (ARR_NDIM(arr) != 1 ||
! 				numcols < 0 ||
! 				ARR_HASNULL(arr) ||
! 				ARR_ELEMTYPE(arr) != INT2OID)
! 				elog(ERROR, "conkey is not a 1-D smallint array");
! 			attnums = (int16 *) ARR_DATA_PTR(arr);
  
! 			/* Construct the result value */
! 			for (i = 0; i < numcols; i++)
! 			{
! 				conattnos = bms_add_member(conattnos,
! 										   attnums[i] - FirstLowInvalidHeapAttributeNumber);
! 			}
  		}
  	}
  
*************** get_relation_idx_constraint_oid(Oid rela
*** 1224,1230 ****
  				BTEqualStrategyNumber,
  				F_OIDEQ,
  				ObjectIdGetDatum(relationId));
! 	scan = systable_beginscan(pg_constraint, ConstraintRelidIndexId,
  							  true, NULL, 1, &key);
  	while ((tuple = systable_getnext(scan)) != NULL)
  	{
--- 1204,1210 ----
  				BTEqualStrategyNumber,
  				F_OIDEQ,
  				ObjectIdGetDatum(relationId));
! 	scan = systable_beginscan(pg_constraint, ConstraintRelidTypidNameIndexId,
  							  true, NULL, 1, &key);
  	while ((tuple = systable_getnext(scan)) != NULL)
  	{
*************** get_domain_constraint_oid(Oid typid, con
*** 1254,1291 ****
  	Relation	pg_constraint;
  	HeapTuple	tuple;
  	SysScanDesc scan;
! 	ScanKeyData skey[1];
  	Oid			conOid = InvalidOid;
  
- 	/*
- 	 * Fetch the constraint tuple from pg_constraint.  There may be more than
- 	 * one match, because constraints are not required to have unique names;
- 	 * if so, error out.
- 	 */
  	pg_constraint = heap_open(ConstraintRelationId, AccessShareLock);
  
  	ScanKeyInit(&skey[0],
  				Anum_pg_constraint_contypid,
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(typid));
  
! 	scan = systable_beginscan(pg_constraint, ConstraintTypidIndexId, true,
! 							  NULL, 1, skey);
! 
! 	while (HeapTupleIsValid(tuple = systable_getnext(scan)))
! 	{
! 		Form_pg_constraint con = (Form_pg_constraint) GETSTRUCT(tuple);
  
! 		if (strcmp(NameStr(con->conname), conname) == 0)
! 		{
! 			if (OidIsValid(conOid))
! 				ereport(ERROR,
! 						(errcode(ERRCODE_DUPLICATE_OBJECT),
! 						 errmsg("domain %s has multiple constraints named \"%s\"",
! 								format_type_be(typid), conname)));
! 			conOid = HeapTupleGetOid(tuple);
! 		}
! 	}
  
  	systable_endscan(scan);
  
--- 1234,1263 ----
  	Relation	pg_constraint;
  	HeapTuple	tuple;
  	SysScanDesc scan;
! 	ScanKeyData skey[3];
  	Oid			conOid = InvalidOid;
  
  	pg_constraint = heap_open(ConstraintRelationId, AccessShareLock);
  
  	ScanKeyInit(&skey[0],
+ 				Anum_pg_constraint_conrelid,
+ 				BTEqualStrategyNumber, F_OIDEQ,
+ 				ObjectIdGetDatum(InvalidOid));
+ 	ScanKeyInit(&skey[1],
  				Anum_pg_constraint_contypid,
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(typid));
+ 	ScanKeyInit(&skey[2],
+ 				Anum_pg_constraint_conname,
+ 				BTEqualStrategyNumber, F_NAMEEQ,
+ 				CStringGetDatum(conname));
  
! 	scan = systable_beginscan(pg_constraint, ConstraintRelidTypidNameIndexId, true,
! 							  NULL, 3, skey);
  
! 	/* There can be at most one matching row */
! 	if (HeapTupleIsValid(tuple = systable_getnext(scan)))
! 		conOid = HeapTupleGetOid(tuple);
  
  	systable_endscan(scan);
  
*************** get_primary_key_attnos(Oid relid, bool d
*** 1335,1341 ****
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(relid));
  
! 	scan = systable_beginscan(pg_constraint, ConstraintRelidIndexId, true,
  							  NULL, 1, skey);
  
  	while (HeapTupleIsValid(tuple = systable_getnext(scan)))
--- 1307,1313 ----
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(relid));
  
! 	scan = systable_beginscan(pg_constraint, ConstraintRelidTypidNameIndexId, true,
  							  NULL, 1, skey);
  
  	while (HeapTupleIsValid(tuple = systable_getnext(scan)))
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index f46af41..a3edef5 100644
*** a/src/backend/commands/tablecmds.c
--- b/src/backend/commands/tablecmds.c
*************** ATExecAlterConstraint(Relation rel, Alte
*** 7801,7810 ****
  	Constraint *cmdcon;
  	Relation	conrel;
  	SysScanDesc scan;
! 	ScanKeyData key;
  	HeapTuple	contuple;
! 	Form_pg_constraint currcon = NULL;
! 	bool		found = false;
  	ObjectAddress address;
  
  	cmdcon = castNode(Constraint, cmd->def);
--- 7801,7809 ----
  	Constraint *cmdcon;
  	Relation	conrel;
  	SysScanDesc scan;
! 	ScanKeyData skey[3];
  	HeapTuple	contuple;
! 	Form_pg_constraint currcon;
  	ObjectAddress address;
  
  	cmdcon = castNode(Constraint, cmd->def);
*************** ATExecAlterConstraint(Relation rel, Alte
*** 7814,7842 ****
  	/*
  	 * Find and check the target constraint
  	 */
! 	ScanKeyInit(&key,
  				Anum_pg_constraint_conrelid,
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(RelationGetRelid(rel)));
! 	scan = systable_beginscan(conrel, ConstraintRelidIndexId,
! 							  true, NULL, 1, &key);
! 
! 	while (HeapTupleIsValid(contuple = systable_getnext(scan)))
! 	{
! 		currcon = (Form_pg_constraint) GETSTRUCT(contuple);
! 		if (strcmp(NameStr(currcon->conname), cmdcon->conname) == 0)
! 		{
! 			found = true;
! 			break;
! 		}
! 	}
  
! 	if (!found)
  		ereport(ERROR,
  				(errcode(ERRCODE_UNDEFINED_OBJECT),
  				 errmsg("constraint \"%s\" of relation \"%s\" does not exist",
  						cmdcon->conname, RelationGetRelationName(rel))));
  
  	if (currcon->contype != CONSTRAINT_FOREIGN)
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
--- 7813,7841 ----
  	/*
  	 * Find and check the target constraint
  	 */
! 	ScanKeyInit(&skey[0],
  				Anum_pg_constraint_conrelid,
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(RelationGetRelid(rel)));
! 	ScanKeyInit(&skey[1],
! 				Anum_pg_constraint_contypid,
! 				BTEqualStrategyNumber, F_OIDEQ,
! 				ObjectIdGetDatum(InvalidOid));
! 	ScanKeyInit(&skey[2],
! 				Anum_pg_constraint_conname,
! 				BTEqualStrategyNumber, F_NAMEEQ,
! 				CStringGetDatum(cmdcon->conname));
! 	scan = systable_beginscan(conrel, ConstraintRelidTypidNameIndexId,
! 							  true, NULL, 3, skey);
  
! 	/* There can be at most one matching row */
! 	if (!HeapTupleIsValid(contuple = systable_getnext(scan)))
  		ereport(ERROR,
  				(errcode(ERRCODE_UNDEFINED_OBJECT),
  				 errmsg("constraint \"%s\" of relation \"%s\" does not exist",
  						cmdcon->conname, RelationGetRelationName(rel))));
  
+ 	currcon = (Form_pg_constraint) GETSTRUCT(contuple);
  	if (currcon->contype != CONSTRAINT_FOREIGN)
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
*************** ATExecValidateConstraint(Relation rel, c
*** 7969,7978 ****
  {
  	Relation	conrel;
  	SysScanDesc scan;
! 	ScanKeyData key;
  	HeapTuple	tuple;
! 	Form_pg_constraint con = NULL;
! 	bool		found = false;
  	ObjectAddress address;
  
  	conrel = heap_open(ConstraintRelationId, RowExclusiveLock);
--- 7968,7976 ----
  {
  	Relation	conrel;
  	SysScanDesc scan;
! 	ScanKeyData skey[3];
  	HeapTuple	tuple;
! 	Form_pg_constraint con;
  	ObjectAddress address;
  
  	conrel = heap_open(ConstraintRelationId, RowExclusiveLock);
*************** ATExecValidateConstraint(Relation rel, c
*** 7980,8008 ****
  	/*
  	 * Find and check the target constraint
  	 */
! 	ScanKeyInit(&key,
  				Anum_pg_constraint_conrelid,
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(RelationGetRelid(rel)));
! 	scan = systable_beginscan(conrel, ConstraintRelidIndexId,
! 							  true, NULL, 1, &key);
! 
! 	while (HeapTupleIsValid(tuple = systable_getnext(scan)))
! 	{
! 		con = (Form_pg_constraint) GETSTRUCT(tuple);
! 		if (strcmp(NameStr(con->conname), constrName) == 0)
! 		{
! 			found = true;
! 			break;
! 		}
! 	}
  
! 	if (!found)
  		ereport(ERROR,
  				(errcode(ERRCODE_UNDEFINED_OBJECT),
  				 errmsg("constraint \"%s\" of relation \"%s\" does not exist",
  						constrName, RelationGetRelationName(rel))));
  
  	if (con->contype != CONSTRAINT_FOREIGN &&
  		con->contype != CONSTRAINT_CHECK)
  		ereport(ERROR,
--- 7978,8006 ----
  	/*
  	 * Find and check the target constraint
  	 */
! 	ScanKeyInit(&skey[0],
  				Anum_pg_constraint_conrelid,
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(RelationGetRelid(rel)));
! 	ScanKeyInit(&skey[1],
! 				Anum_pg_constraint_contypid,
! 				BTEqualStrategyNumber, F_OIDEQ,
! 				ObjectIdGetDatum(InvalidOid));
! 	ScanKeyInit(&skey[2],
! 				Anum_pg_constraint_conname,
! 				BTEqualStrategyNumber, F_NAMEEQ,
! 				CStringGetDatum(constrName));
! 	scan = systable_beginscan(conrel, ConstraintRelidTypidNameIndexId,
! 							  true, NULL, 3, skey);
  
! 	/* There can be at most one matching row */
! 	if (!HeapTupleIsValid(tuple = systable_getnext(scan)))
  		ereport(ERROR,
  				(errcode(ERRCODE_UNDEFINED_OBJECT),
  				 errmsg("constraint \"%s\" of relation \"%s\" does not exist",
  						constrName, RelationGetRelationName(rel))));
  
+ 	con = (Form_pg_constraint) GETSTRUCT(tuple);
  	if (con->contype != CONSTRAINT_FOREIGN &&
  		con->contype != CONSTRAINT_CHECK)
  		ereport(ERROR,
*************** ATExecDropConstraint(Relation rel, const
*** 8865,8871 ****
  	Relation	conrel;
  	Form_pg_constraint con;
  	SysScanDesc scan;
! 	ScanKeyData key;
  	HeapTuple	tuple;
  	bool		found = false;
  	bool		is_no_inherit_constraint = false;
--- 8863,8869 ----
  	Relation	conrel;
  	Form_pg_constraint con;
  	SysScanDesc scan;
! 	ScanKeyData skey[3];
  	HeapTuple	tuple;
  	bool		found = false;
  	bool		is_no_inherit_constraint = false;
*************** ATExecDropConstraint(Relation rel, const
*** 8879,8900 ****
  	/*
  	 * Find and drop the target constraint
  	 */
! 	ScanKeyInit(&key,
  				Anum_pg_constraint_conrelid,
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(RelationGetRelid(rel)));
! 	scan = systable_beginscan(conrel, ConstraintRelidIndexId,
! 							  true, NULL, 1, &key);
  
! 	while (HeapTupleIsValid(tuple = systable_getnext(scan)))
  	{
  		ObjectAddress conobj;
  
  		con = (Form_pg_constraint) GETSTRUCT(tuple);
  
- 		if (strcmp(NameStr(con->conname), constrName) != 0)
- 			continue;
- 
  		/* Don't drop inherited constraints */
  		if (con->coninhcount > 0 && !recursing)
  			ereport(ERROR,
--- 8877,8904 ----
  	/*
  	 * Find and drop the target constraint
  	 */
! 	ScanKeyInit(&skey[0],
  				Anum_pg_constraint_conrelid,
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(RelationGetRelid(rel)));
! 	ScanKeyInit(&skey[1],
! 				Anum_pg_constraint_contypid,
! 				BTEqualStrategyNumber, F_OIDEQ,
! 				ObjectIdGetDatum(InvalidOid));
! 	ScanKeyInit(&skey[2],
! 				Anum_pg_constraint_conname,
! 				BTEqualStrategyNumber, F_NAMEEQ,
! 				CStringGetDatum(constrName));
! 	scan = systable_beginscan(conrel, ConstraintRelidTypidNameIndexId,
! 							  true, NULL, 3, skey);
  
! 	/* There can be at most one matching row */
! 	if (HeapTupleIsValid(tuple = systable_getnext(scan)))
  	{
  		ObjectAddress conobj;
  
  		con = (Form_pg_constraint) GETSTRUCT(tuple);
  
  		/* Don't drop inherited constraints */
  		if (con->coninhcount > 0 && !recursing)
  			ereport(ERROR,
*************** ATExecDropConstraint(Relation rel, const
*** 8932,8940 ****
  		performDeletion(&conobj, behavior, 0);
  
  		found = true;
- 
- 		/* constraint found and dropped -- no need to keep looping */
- 		break;
  	}
  
  	systable_endscan(scan);
--- 8936,8941 ----
*************** ATExecDropConstraint(Relation rel, const
*** 8990,9016 ****
  		childrel = heap_open(childrelid, NoLock);
  		CheckTableNotInUse(childrel, "ALTER TABLE");
  
! 		ScanKeyInit(&key,
  					Anum_pg_constraint_conrelid,
  					BTEqualStrategyNumber, F_OIDEQ,
  					ObjectIdGetDatum(childrelid));
! 		scan = systable_beginscan(conrel, ConstraintRelidIndexId,
! 								  true, NULL, 1, &key);
! 
! 		/* scan for matching tuple - there should only be one */
! 		while (HeapTupleIsValid(tuple = systable_getnext(scan)))
! 		{
! 			con = (Form_pg_constraint) GETSTRUCT(tuple);
! 
! 			/* Right now only CHECK constraints can be inherited */
! 			if (con->contype != CONSTRAINT_CHECK)
! 				continue;
! 
! 			if (strcmp(NameStr(con->conname), constrName) == 0)
! 				break;
! 		}
  
! 		if (!HeapTupleIsValid(tuple))
  			ereport(ERROR,
  					(errcode(ERRCODE_UNDEFINED_OBJECT),
  					 errmsg("constraint \"%s\" of relation \"%s\" does not exist",
--- 8991,9013 ----
  		childrel = heap_open(childrelid, NoLock);
  		CheckTableNotInUse(childrel, "ALTER TABLE");
  
! 		ScanKeyInit(&skey[0],
  					Anum_pg_constraint_conrelid,
  					BTEqualStrategyNumber, F_OIDEQ,
  					ObjectIdGetDatum(childrelid));
! 		ScanKeyInit(&skey[1],
! 					Anum_pg_constraint_contypid,
! 					BTEqualStrategyNumber, F_OIDEQ,
! 					ObjectIdGetDatum(InvalidOid));
! 		ScanKeyInit(&skey[2],
! 					Anum_pg_constraint_conname,
! 					BTEqualStrategyNumber, F_NAMEEQ,
! 					CStringGetDatum(constrName));
! 		scan = systable_beginscan(conrel, ConstraintRelidTypidNameIndexId,
! 								  true, NULL, 3, skey);
  
! 		/* There can be at most one matching row */
! 		if (!HeapTupleIsValid(tuple = systable_getnext(scan)))
  			ereport(ERROR,
  					(errcode(ERRCODE_UNDEFINED_OBJECT),
  					 errmsg("constraint \"%s\" of relation \"%s\" does not exist",
*************** ATExecDropConstraint(Relation rel, const
*** 9023,9028 ****
--- 9020,9029 ----
  
  		con = (Form_pg_constraint) GETSTRUCT(copy_tuple);
  
+ 		/* Right now only CHECK constraints can be inherited */
+ 		if (con->contype != CONSTRAINT_CHECK)
+ 			elog(ERROR, "inherited constraint is not a CHECK constraint");
+ 
  		if (con->coninhcount <= 0)	/* shouldn't happen */
  			elog(ERROR, "relation %u has non-inherited constraint \"%s\"",
  				 childrelid, constrName);
*************** MergeConstraintsIntoExisting(Relation ch
*** 11824,11830 ****
  				Anum_pg_constraint_conrelid,
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(RelationGetRelid(parent_rel)));
! 	parent_scan = systable_beginscan(catalog_relation, ConstraintRelidIndexId,
  									 true, NULL, 1, &parent_key);
  
  	while (HeapTupleIsValid(parent_tuple = systable_getnext(parent_scan)))
--- 11825,11831 ----
  				Anum_pg_constraint_conrelid,
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(RelationGetRelid(parent_rel)));
! 	parent_scan = systable_beginscan(catalog_relation, ConstraintRelidTypidNameIndexId,
  									 true, NULL, 1, &parent_key);
  
  	while (HeapTupleIsValid(parent_tuple = systable_getnext(parent_scan)))
*************** MergeConstraintsIntoExisting(Relation ch
*** 11847,11853 ****
  					Anum_pg_constraint_conrelid,
  					BTEqualStrategyNumber, F_OIDEQ,
  					ObjectIdGetDatum(RelationGetRelid(child_rel)));
! 		child_scan = systable_beginscan(catalog_relation, ConstraintRelidIndexId,
  										true, NULL, 1, &child_key);
  
  		while (HeapTupleIsValid(child_tuple = systable_getnext(child_scan)))
--- 11848,11854 ----
  					Anum_pg_constraint_conrelid,
  					BTEqualStrategyNumber, F_OIDEQ,
  					ObjectIdGetDatum(RelationGetRelid(child_rel)));
! 		child_scan = systable_beginscan(catalog_relation, ConstraintRelidTypidNameIndexId,
  										true, NULL, 1, &child_key);
  
  		while (HeapTupleIsValid(child_tuple = systable_getnext(child_scan)))
*************** RemoveInheritance(Relation child_rel, Re
*** 12068,12074 ****
  				Anum_pg_constraint_conrelid,
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(RelationGetRelid(parent_rel)));
! 	scan = systable_beginscan(catalogRelation, ConstraintRelidIndexId,
  							  true, NULL, 1, key);
  
  	connames = NIL;
--- 12069,12075 ----
  				Anum_pg_constraint_conrelid,
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(RelationGetRelid(parent_rel)));
! 	scan = systable_beginscan(catalogRelation, ConstraintRelidTypidNameIndexId,
  							  true, NULL, 1, key);
  
  	connames = NIL;
*************** RemoveInheritance(Relation child_rel, Re
*** 12088,12094 ****
  				Anum_pg_constraint_conrelid,
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(RelationGetRelid(child_rel)));
! 	scan = systable_beginscan(catalogRelation, ConstraintRelidIndexId,
  							  true, NULL, 1, key);
  
  	while (HeapTupleIsValid(constraintTuple = systable_getnext(scan)))
--- 12089,12095 ----
  				Anum_pg_constraint_conrelid,
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(RelationGetRelid(child_rel)));
! 	scan = systable_beginscan(catalogRelation, ConstraintRelidTypidNameIndexId,
  							  true, NULL, 1, key);
  
  	while (HeapTupleIsValid(constraintTuple = systable_getnext(scan)))
*************** ATPrepChangePersistence(Relation rel, bo
*** 12829,12835 ****
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(RelationGetRelid(rel)));
  	scan = systable_beginscan(pg_constraint,
! 							  toLogged ? ConstraintRelidIndexId : InvalidOid,
  							  true, NULL, 1, skey);
  
  	while (HeapTupleIsValid(tuple = systable_getnext(scan)))
--- 12830,12836 ----
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(RelationGetRelid(rel)));
  	scan = systable_beginscan(pg_constraint,
! 							  toLogged ? ConstraintRelidTypidNameIndexId : InvalidOid,
  							  true, NULL, 1, skey);
  
  	while (HeapTupleIsValid(tuple = systable_getnext(scan)))
diff --git a/src/backend/commands/typecmds.c b/src/backend/commands/typecmds.c
index 175ecc8..a67f9ce 100644
*** a/src/backend/commands/typecmds.c
--- b/src/backend/commands/typecmds.c
*************** AlterDomainNotNull(List *names, bool not
*** 2444,2449 ****
--- 2444,2451 ----
   * AlterDomainDropConstraint
   *
   * Implements the ALTER DOMAIN DROP CONSTRAINT statement
+  *
+  * Returns ObjectAddress of the modified domain.
   */
  ObjectAddress
  AlterDomainDropConstraint(List *names, const char *constrName,
*************** AlterDomainDropConstraint(List *names, c
*** 2455,2464 ****
  	Relation	rel;
  	Relation	conrel;
  	SysScanDesc conscan;
! 	ScanKeyData key[1];
  	HeapTuple	contup;
  	bool		found = false;
! 	ObjectAddress address = InvalidObjectAddress;
  
  	/* Make a TypeName so we can use standard type lookup machinery */
  	typename = makeTypeNameFromNameList(names);
--- 2457,2466 ----
  	Relation	rel;
  	Relation	conrel;
  	SysScanDesc conscan;
! 	ScanKeyData skey[3];
  	HeapTuple	contup;
  	bool		found = false;
! 	ObjectAddress address;
  
  	/* Make a TypeName so we can use standard type lookup machinery */
  	typename = makeTypeNameFromNameList(names);
*************** AlterDomainDropConstraint(List *names, c
*** 2477,2513 ****
  	/* Grab an appropriate lock on the pg_constraint relation */
  	conrel = heap_open(ConstraintRelationId, RowExclusiveLock);
  
! 	/* Use the index to scan only constraints of the target relation */
! 	ScanKeyInit(&key[0],
  				Anum_pg_constraint_contypid,
  				BTEqualStrategyNumber, F_OIDEQ,
! 				ObjectIdGetDatum(HeapTupleGetOid(tup)));
  
! 	conscan = systable_beginscan(conrel, ConstraintTypidIndexId, true,
! 								 NULL, 1, key);
  
! 	/*
! 	 * Scan over the result set, removing any matching entries.
! 	 */
! 	while ((contup = systable_getnext(conscan)) != NULL)
  	{
! 		Form_pg_constraint con = (Form_pg_constraint) GETSTRUCT(contup);
! 
! 		if (strcmp(NameStr(con->conname), constrName) == 0)
! 		{
! 			ObjectAddress conobj;
  
! 			conobj.classId = ConstraintRelationId;
! 			conobj.objectId = HeapTupleGetOid(contup);
! 			conobj.objectSubId = 0;
  
! 			performDeletion(&conobj, behavior, 0);
! 			found = true;
! 		}
  	}
  
- 	ObjectAddressSet(address, TypeRelationId, domainoid);
- 
  	/* Clean up after the scan */
  	systable_endscan(conscan);
  	heap_close(conrel, RowExclusiveLock);
--- 2479,2514 ----
  	/* Grab an appropriate lock on the pg_constraint relation */
  	conrel = heap_open(ConstraintRelationId, RowExclusiveLock);
  
! 	/* Find and remove the target constraint */
! 	ScanKeyInit(&skey[0],
! 				Anum_pg_constraint_conrelid,
! 				BTEqualStrategyNumber, F_OIDEQ,
! 				ObjectIdGetDatum(InvalidOid));
! 	ScanKeyInit(&skey[1],
  				Anum_pg_constraint_contypid,
  				BTEqualStrategyNumber, F_OIDEQ,
! 				ObjectIdGetDatum(domainoid));
! 	ScanKeyInit(&skey[2],
! 				Anum_pg_constraint_conname,
! 				BTEqualStrategyNumber, F_NAMEEQ,
! 				CStringGetDatum(constrName));
  
! 	conscan = systable_beginscan(conrel, ConstraintRelidTypidNameIndexId, true,
! 								 NULL, 3, skey);
  
! 	/* There can be at most one matching row */
! 	if ((contup = systable_getnext(conscan)) != NULL)
  	{
! 		ObjectAddress conobj;
  
! 		conobj.classId = ConstraintRelationId;
! 		conobj.objectId = HeapTupleGetOid(contup);
! 		conobj.objectSubId = 0;
  
! 		performDeletion(&conobj, behavior, 0);
! 		found = true;
  	}
  
  	/* Clean up after the scan */
  	systable_endscan(conscan);
  	heap_close(conrel, RowExclusiveLock);
*************** AlterDomainDropConstraint(List *names, c
*** 2527,2532 ****
--- 2528,2535 ----
  							constrName, TypeNameToString(typename))));
  	}
  
+ 	ObjectAddressSet(address, TypeRelationId, domainoid);
+ 
  	return address;
  }
  
*************** AlterDomainValidateConstraint(List *name
*** 2652,2667 ****
  	Relation	typrel;
  	Relation	conrel;
  	HeapTuple	tup;
! 	Form_pg_constraint con = NULL;
  	Form_pg_constraint copy_con;
  	char	   *conbin;
  	SysScanDesc scan;
  	Datum		val;
- 	bool		found = false;
  	bool		isnull;
  	HeapTuple	tuple;
  	HeapTuple	copyTuple;
! 	ScanKeyData key;
  	ObjectAddress address;
  
  	/* Make a TypeName so we can use standard type lookup machinery */
--- 2655,2669 ----
  	Relation	typrel;
  	Relation	conrel;
  	HeapTuple	tup;
! 	Form_pg_constraint con;
  	Form_pg_constraint copy_con;
  	char	   *conbin;
  	SysScanDesc scan;
  	Datum		val;
  	bool		isnull;
  	HeapTuple	tuple;
  	HeapTuple	copyTuple;
! 	ScanKeyData skey[3];
  	ObjectAddress address;
  
  	/* Make a TypeName so we can use standard type lookup machinery */
*************** AlterDomainValidateConstraint(List *name
*** 2682,2710 ****
  	 * Find and check the target constraint
  	 */
  	conrel = heap_open(ConstraintRelationId, RowExclusiveLock);
! 	ScanKeyInit(&key,
  				Anum_pg_constraint_contypid,
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(domainoid));
! 	scan = systable_beginscan(conrel, ConstraintTypidIndexId,
! 							  true, NULL, 1, &key);
  
! 	while (HeapTupleIsValid(tuple = systable_getnext(scan)))
! 	{
! 		con = (Form_pg_constraint) GETSTRUCT(tuple);
! 		if (strcmp(NameStr(con->conname), constrName) == 0)
! 		{
! 			found = true;
! 			break;
! 		}
! 	}
  
! 	if (!found)
  		ereport(ERROR,
  				(errcode(ERRCODE_UNDEFINED_OBJECT),
  				 errmsg("constraint \"%s\" of domain \"%s\" does not exist",
  						constrName, TypeNameToString(typename))));
  
  	if (con->contype != CONSTRAINT_CHECK)
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
--- 2684,2714 ----
  	 * Find and check the target constraint
  	 */
  	conrel = heap_open(ConstraintRelationId, RowExclusiveLock);
! 
! 	ScanKeyInit(&skey[0],
! 				Anum_pg_constraint_conrelid,
! 				BTEqualStrategyNumber, F_OIDEQ,
! 				ObjectIdGetDatum(InvalidOid));
! 	ScanKeyInit(&skey[1],
  				Anum_pg_constraint_contypid,
  				BTEqualStrategyNumber, F_OIDEQ,
  				ObjectIdGetDatum(domainoid));
! 	ScanKeyInit(&skey[2],
! 				Anum_pg_constraint_conname,
! 				BTEqualStrategyNumber, F_NAMEEQ,
! 				CStringGetDatum(constrName));
  
! 	scan = systable_beginscan(conrel, ConstraintRelidTypidNameIndexId, true,
! 							  NULL, 3, skey);
  
! 	/* There can be at most one matching row */
! 	if (!HeapTupleIsValid(tuple = systable_getnext(scan)))
  		ereport(ERROR,
  				(errcode(ERRCODE_UNDEFINED_OBJECT),
  				 errmsg("constraint \"%s\" of domain \"%s\" does not exist",
  						constrName, TypeNameToString(typename))));
  
+ 	con = (Form_pg_constraint) GETSTRUCT(tuple);
  	if (con->contype != CONSTRAINT_CHECK)
  		ereport(ERROR,
  				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
diff --git a/src/backend/utils/cache/relcache.c b/src/backend/utils/cache/relcache.c
index 6125421..a4fc001 100644
*** a/src/backend/utils/cache/relcache.c
--- b/src/backend/utils/cache/relcache.c
*************** CheckConstraintFetch(Relation relation)
*** 4016,4022 ****
  				ObjectIdGetDatum(RelationGetRelid(relation)));
  
  	conrel = heap_open(ConstraintRelationId, AccessShareLock);
! 	conscan = systable_beginscan(conrel, ConstraintRelidIndexId, true,
  								 NULL, 1, skey);
  
  	while (HeapTupleIsValid(htup = systable_getnext(conscan)))
--- 4016,4022 ----
  				ObjectIdGetDatum(RelationGetRelid(relation)));
  
  	conrel = heap_open(ConstraintRelationId, AccessShareLock);
! 	conscan = systable_beginscan(conrel, ConstraintRelidTypidNameIndexId, true,
  								 NULL, 1, skey);
  
  	while (HeapTupleIsValid(htup = systable_getnext(conscan)))
*************** RelationGetFKeyList(Relation relation)
*** 4127,4133 ****
  				ObjectIdGetDatum(RelationGetRelid(relation)));
  
  	conrel = heap_open(ConstraintRelationId, AccessShareLock);
! 	conscan = systable_beginscan(conrel, ConstraintRelidIndexId, true,
  								 NULL, 1, &skey);
  
  	while (HeapTupleIsValid(htup = systable_getnext(conscan)))
--- 4127,4133 ----
  				ObjectIdGetDatum(RelationGetRelid(relation)));
  
  	conrel = heap_open(ConstraintRelationId, AccessShareLock);
! 	conscan = systable_beginscan(conrel, ConstraintRelidTypidNameIndexId, true,
  								 NULL, 1, &skey);
  
  	while (HeapTupleIsValid(htup = systable_getnext(conscan)))
*************** RelationGetExclusionInfo(Relation indexR
*** 5105,5110 ****
--- 5105,5114 ----
  	 * Search pg_constraint for the constraint associated with the index. To
  	 * make this not too painfully slow, we use the index on conrelid; that
  	 * will hold the parent relation's OID not the index's own OID.
+ 	 *
+ 	 * Note: if we wanted to rely on the constraint name matching the index's
+ 	 * name, we could just do a direct lookup using pg_constraint's unique
+ 	 * index.  For the moment it doesn't seem worth requiring that.
  	 */
  	ScanKeyInit(&skey[0],
  				Anum_pg_constraint_conrelid,
*************** RelationGetExclusionInfo(Relation indexR
*** 5112,5118 ****
  				ObjectIdGetDatum(indexRelation->rd_index->indrelid));
  
  	conrel = heap_open(ConstraintRelationId, AccessShareLock);
! 	conscan = systable_beginscan(conrel, ConstraintRelidIndexId, true,
  								 NULL, 1, skey);
  	found = false;
  
--- 5116,5122 ----
  				ObjectIdGetDatum(indexRelation->rd_index->indrelid));
  
  	conrel = heap_open(ConstraintRelationId, AccessShareLock);
! 	conscan = systable_beginscan(conrel, ConstraintRelidTypidNameIndexId, true,
  								 NULL, 1, skey);
  	found = false;
  
diff --git a/src/include/catalog/indexing.h b/src/include/catalog/indexing.h
index 2491582..254fbef 100644
*** a/src/include/catalog/indexing.h
--- b/src/include/catalog/indexing.h
*************** DECLARE_UNIQUE_INDEX(pg_collation_oid_in
*** 121,128 ****
  
  DECLARE_INDEX(pg_constraint_conname_nsp_index, 2664, on pg_constraint using btree(conname name_ops, connamespace oid_ops));
  #define ConstraintNameNspIndexId  2664
! DECLARE_INDEX(pg_constraint_conrelid_index, 2665, on pg_constraint using btree(conrelid oid_ops));
! #define ConstraintRelidIndexId	2665
  DECLARE_INDEX(pg_constraint_contypid_index, 2666, on pg_constraint using btree(contypid oid_ops));
  #define ConstraintTypidIndexId	2666
  DECLARE_UNIQUE_INDEX(pg_constraint_oid_index, 2667, on pg_constraint using btree(oid oid_ops));
--- 121,128 ----
  
  DECLARE_INDEX(pg_constraint_conname_nsp_index, 2664, on pg_constraint using btree(conname name_ops, connamespace oid_ops));
  #define ConstraintNameNspIndexId  2664
! DECLARE_UNIQUE_INDEX(pg_constraint_conrelid_contypid_conname_index, 2665, on pg_constraint using btree(conrelid oid_ops, contypid oid_ops, conname name_ops));
! #define ConstraintRelidTypidNameIndexId	2665
  DECLARE_INDEX(pg_constraint_contypid_index, 2666, on pg_constraint using btree(contypid oid_ops));
  #define ConstraintTypidIndexId	2666
  DECLARE_UNIQUE_INDEX(pg_constraint_oid_index, 2667, on pg_constraint using btree(oid oid_ops));
diff --git a/src/include/catalog/pg_constraint.h b/src/include/catalog/pg_constraint.h
index 7c1c0e1..4435310 100644
*** a/src/include/catalog/pg_constraint.h
--- b/src/include/catalog/pg_constraint.h
*************** CATALOG(pg_constraint,2606,ConstraintRel
*** 39,44 ****
--- 39,48 ----
  	 * global lock to generate a globally unique name for a nameless
  	 * constraint.  We associate a namespace with constraint names only for
  	 * SQL-spec compatibility.
+ 	 *
+ 	 * However, we do require conname to be unique among the constraints of a
+ 	 * single relation or domain.  This is enforced by a unique index on
+ 	 * conrelid + contypid + conname.
  	 */
  	NameData	conname;		/* name of this constraint */
  	Oid			connamespace;	/* OID of namespace containing constraint */