Allow ALTER TABLE ... ALTER CONSTRAINT ... RENAME

Joachim Wieland

src/backend/catalog/pg_constraint.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/catalog/pg_constraint.c,v 1.28 2005/11/22 18:17:08 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/catalog/pg_constraint.c,v 1.29 2006/02/11 22:17:18 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -664,3 +664,191 @@ AlterConstraintNamespaces(Oid ownerId, Oid oldNspId,
 
 	heap_close(conRel, RowExclusiveLock);
 }
+
+
+/*
+ * RenameConstraint
+ *		Rename a single constraint record
+ *		conId: The OID of the constraint to rename
+ *		newName: The new name of the constraint
+ *		implicitRename: is this an implicit rename? If so, we will issue
+ *		                a notice about the implicit rename
+ *		cmdName: the command that triggered the rename for the "implicitly
+ *		         renames" notice message
+ */
+void
+RenameConstraint(Oid conId, const char* newName,
+				 bool implicitRename, const char* cmdName)
+{
+	Relation			conRel;
+	ScanKeyData 		key[1];
+	SysScanDesc 		scan;
+	HeapTuple 			tup;
+	NameData			newNameData;
+	Relation			rel;
+	Oid					relId;
+	Oid					nspOid;
+	Form_pg_constraint	conform;
+
+	/* before reading the tuple, lock the table it constraints in
+	 * AccessExclusiveLock mode. Otherwise, if we read it before locking this
+	 * table, the tuple might be changed by another transaction and our copy
+	 * would be out of date
+	 */
+	relId = GetConstraintRelationId(conId);
+	if (!OidIsValid(relId))
+	{
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("constraint with OID %d does not exist", conId)));
+	}
+
+	rel = relation_open(relId, AccessExclusiveLock);
+	nspOid = get_rel_namespace(relId);
+
+	conRel = heap_open(ConstraintRelationId, RowExclusiveLock);
+
+	ScanKeyInit(&key[0],
+				ObjectIdAttributeNumber,
+				BTEqualStrategyNumber, F_OIDEQ,
+				ObjectIdGetDatum(conId));
+
+	scan = systable_beginscan(conRel, ConstraintOidIndexId, true,
+							  SnapshotNow, 1, key);
+	if (!HeapTupleIsValid((tup = systable_getnext(scan))))
+	{
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("constraint with OID %d does not exist", conId)));
+	}
+
+	conform = (Form_pg_constraint) GETSTRUCT(tup);
+
+	if (ConstraintNameIsUsed(CONSTRAINT_RELATION,
+							 conform->conrelid,
+							 get_rel_namespace(conform->conrelid),
+							 newName))
+	{
+		ereport(ERROR,
+				(errcode(ERRCODE_DUPLICATE_OBJECT),
+				 errmsg("constraint \"%s\" for relation \"%s\" already exists",
+						newName,
+						RelationGetRelationName(rel))));
+	}
+	tup = heap_copytuple(tup);
+	conform = (Form_pg_constraint) GETSTRUCT(tup);
+
+	if (implicitRename && cmdName)
+	{
+		ereport(NOTICE,
+				(errmsg("%s will implicitly rename constraint "
+						"\"%s\" to \"%s\" on table \"%s.%s\"",
+					cmdName,
+					NameStr(conform->conname),
+					newName,
+					get_namespace_name(nspOid),
+					RelationGetRelationName(rel))));
+	}
+
+	namestrcpy(&newNameData, newName);
+	conform->conname = newNameData;
+
+	simple_heap_update(conRel, &tup->t_self, tup);
+	CatalogUpdateIndexes(conRel, tup);
+	heap_freetuple(tup);
+
+	systable_endscan(scan);
+	heap_close(conRel, RowExclusiveLock);
+
+	/* close relation but hold lock until end of transaction */
+	relation_close(rel, NoLock);
+}
+
+
+/* GetRelationConstraintOid
+ *
+ * Get the contraint OID by the relation Id of the relation it constraints and
+ * this relations' name. We need this function in order to rename a constraint.
+ * This is done via "ALTER TABLE ... ALTER CONSTRAINT name" and the parser
+ * gives us the relation this constraint is defined on as well as the
+ * constraint's name.
+ *
+ * The function returns:
+ *
+ *  - the unique OID of the constraint if the constraint could be found
+ *  - the invalid OID if the constraint was not found
+ *
+ */
+Oid GetRelationConstraintOid(Oid relId, const char* name)
+{
+	Relation		conRel;
+	ScanKeyData 	key[1];
+	SysScanDesc 	scan;
+	HeapTuple 		tup;
+	Oid				conId = InvalidOid;
+
+	/* we don't change data, so an AccessShareLock is enough */
+	conRel = heap_open(ConstraintRelationId, AccessShareLock);
+
+	ScanKeyInit(&key[0],
+				Anum_pg_constraint_conrelid,
+				BTEqualStrategyNumber, F_OIDEQ,
+				ObjectIdGetDatum(relId));
+
+	scan = systable_beginscan(conRel, ConstraintRelidIndexId, true,
+							  SnapshotNow, 1, key);
+
+	while (HeapTupleIsValid((tup = systable_getnext(scan))))
+	{
+		Form_pg_constraint con = (Form_pg_constraint) GETSTRUCT(tup);
+		if (pg_strcasecmp(name, NameStr(con->conname)) == 0)
+		{
+			conId = HeapTupleGetOid(tup);
+			Assert(OidIsValid(conId));
+		}
+	}
+
+	systable_endscan(scan);
+	heap_close(conRel, AccessShareLock);
+
+	return conId;
+}
+
+
+/* GetConstraintRelationId
+ *
+ * Gets the OID of the relation where the constraint is defined on or the
+ * invalid OID if the constraint cannot be found.
+ */
+Oid GetConstraintRelationId(Oid conId)
+{
+	Relation		conRel;
+	ScanKeyData 	key[1];
+	SysScanDesc 	scan;
+	HeapTuple 		tup;
+	Oid				relId = InvalidOid;
+
+	/* we don't change data, so an AccessShareLock is enough */
+	conRel = heap_open(ConstraintRelationId, AccessShareLock);
+
+	ScanKeyInit(&key[0],
+				ObjectIdAttributeNumber,
+				BTEqualStrategyNumber, F_OIDEQ,
+				ObjectIdGetDatum(conId));
+
+	scan = systable_beginscan(conRel, ConstraintOidIndexId, true,
+							  SnapshotNow, 1, key);
+
+	if (HeapTupleIsValid((tup = systable_getnext(scan))))
+	{
+		Form_pg_constraint con = (Form_pg_constraint) GETSTRUCT(tup);
+		relId = con->conrelid;
+		Assert(OidIsValid(relId));
+	}
+
+	systable_endscan(scan);
+	heap_close(conRel, AccessShareLock);
+
+	return relId;
+}
+

src/backend/catalog/pg_depend.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/catalog/pg_depend.c,v 1.17 2005/11/22 18:17:08 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/catalog/pg_depend.c,v 1.18 2006/02/11 22:17:18 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -361,3 +361,102 @@ isObjectPinned(const ObjectAddress *object, Relation rel)
 
 	return ret;
 }
+
+List* getReferencingOids(Oid refClassId, Oid refObjId, Oid refObjSubId,
+						 Oid classId, DependencyType deptype)
+{
+	ScanKeyData		key[3];
+	SysScanDesc		scan;
+	HeapTuple		tup;
+	Relation		depRel;
+	List		   *list = NIL;
+
+	depRel = heap_open(DependRelationId, AccessShareLock);
+
+	ScanKeyInit(&key[0],
+				Anum_pg_depend_refclassid,
+				BTEqualStrategyNumber, F_OIDEQ,
+				ObjectIdGetDatum(refClassId));
+
+	ScanKeyInit(&key[1],
+				Anum_pg_depend_refobjid,
+				BTEqualStrategyNumber, F_OIDEQ,
+				ObjectIdGetDatum(refObjId));
+
+	ScanKeyInit(&key[2],
+				Anum_pg_depend_refobjsubid,
+				BTEqualStrategyNumber, F_OIDEQ,
+				ObjectIdGetDatum(refObjSubId));
+
+	scan = systable_beginscan(depRel, DependReferenceIndexId, true,
+							  SnapshotNow, 3, key);
+
+	while (HeapTupleIsValid(tup = systable_getnext(scan)))
+	{
+		Form_pg_depend	depForm = (Form_pg_depend) GETSTRUCT(tup);
+
+		/* check if the class id is what we want */
+		if (depForm->classid != classId)
+			continue;
+
+		/* check if the DependencyType is what we want */
+		if (depForm->deptype != deptype)
+			continue;
+
+		/* if we are still here, we have found a match */
+		list = lcons_oid(depForm->objid, list);
+		break;
+	}
+	systable_endscan(scan);
+
+	heap_close(depRel, AccessShareLock);
+	return list;
+}
+
+
+List* getDependentOids(Oid classId, Oid objId,
+					   Oid refClassId, DependencyType deptype)
+{
+	ScanKeyData		key[2];
+	SysScanDesc		scan;
+	HeapTuple		tup;
+	Relation		depRel;
+	List		   *list = NIL;
+
+	depRel = heap_open(DependRelationId, AccessShareLock);
+
+	ScanKeyInit(&key[0],
+				Anum_pg_depend_classid,
+				BTEqualStrategyNumber, F_OIDEQ,
+				ObjectIdGetDatum(classId));
+
+	ScanKeyInit(&key[1],
+				Anum_pg_depend_objid,
+				BTEqualStrategyNumber, F_OIDEQ,
+				ObjectIdGetDatum(objId));
+
+	scan = systable_beginscan(depRel, DependDependerIndexId, true,
+							  SnapshotNow, 2, key);
+
+	while (HeapTupleIsValid(tup = systable_getnext(scan)))
+	{
+		Form_pg_depend	depForm = (Form_pg_depend) GETSTRUCT(tup);
+
+		/* check if the DependencyType is what we want */
+		if (depForm->deptype != deptype)
+			continue;
+
+		/* check if the referenced class id is what we want */
+		if (depForm->refclassid != refClassId)
+			continue;
+
+		/* if we are still here, we have found a match */
+		list = lcons_oid(depForm->refobjid, list);
+		break;
+	}
+	systable_endscan(scan);
+
+	heap_close(depRel, AccessShareLock);
+	return list;
+}
+

src/backend/commands/alter.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/commands/alter.c,v 1.15 2005/10/15 02:49:14 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/commands/alter.c,v 1.16 2006/02/11 22:17:18 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -16,8 +16,10 @@
 
 #include "access/htup.h"
 #include "catalog/catalog.h"
+#include "catalog/dependency.h"
 #include "catalog/namespace.h"
 #include "catalog/pg_class.h"
+#include "catalog/pg_constraint.h"
 #include "commands/alter.h"
 #include "commands/conversioncmds.h"
 #include "commands/dbcommands.h"
@@ -88,6 +90,7 @@ ExecRenameStmt(RenameStmt *stmt)
 		case OBJECT_INDEX:
 		case OBJECT_COLUMN:
 		case OBJECT_TRIGGER:
+		case OBJECT_CONSTRAINT:
 			{
 				Oid			relid;
 
@@ -109,12 +112,38 @@ ExecRenameStmt(RenameStmt *stmt)
 							AclResult	aclresult;
 
 							aclresult = pg_namespace_aclcheck(namespaceId,
-															  GetUserId(),
-															  ACL_CREATE);
+													GetUserId(), ACL_CREATE);
 							if (aclresult != ACLCHECK_OK)
 								aclcheck_error(aclresult, ACL_KIND_NAMESPACE,
 											get_namespace_name(namespaceId));
 
+							/*
+							 *	Do NOT refer to stmt->renameType here because
+							 *	you can also rename an index with ALTER TABLE
+							 */
+							if (get_rel_relkind(relid) == RELKIND_INDEX)
+							{
+								/* see if we depend on a constraint */
+								List* depOids = getDependentOids(
+												RelationRelationId, relid,
+												ConstraintRelationId,
+												DEPENDENCY_INTERNAL);
+
+								/* there should only be one constraint */
+								Assert(list_length(depOids) <= 1);
+								if (list_length(depOids) == 1)
+								{
+										Oid conRelId = linitial_oid(depOids);
+										/*
+										 *	Apply the same name to the
+										 *	constraint and tell it that this
+										 *	is an implicit rename triggered
+										 *	by an "ALTER INDEX" command.
+										 */
+										RenameConstraint(conRelId,
+											stmt->newname, true, "ALTER INDEX");
+								}
+							}
 							renamerel(relid, stmt->newname);
 							break;
 						}
@@ -130,6 +159,52 @@ ExecRenameStmt(RenameStmt *stmt)
 								   stmt->subname,		/* old att name */
 								   stmt->newname);		/* new att name */
 						break;
+					case OBJECT_CONSTRAINT:
+						/* XXX could do extra function renameconstr() - but I
+						 * don't know where it should go */
+						/* renameconstr(relid,
+									 stmt->subname,
+									 stmt->newname); */
+						{
+							List		*depRelOids;
+							ListCell	*l;
+							Oid conId =
+									GetRelationConstraintOid(relid,
+															 stmt->subname);
+							if (!OidIsValid(conId)) {
+								ereport(ERROR,
+										(errcode(ERRCODE_UNDEFINED_OBJECT),
+										 errmsg("constraint with name \"%s\" "
+												"does not exist",
+												stmt->subname)));
+							}
+							RenameConstraint(conId, stmt->newname,
+											 false, NULL);
+							depRelOids = getReferencingOids(
+											ConstraintRelationId, conId, 0,
+											RelationRelationId,
+											DEPENDENCY_INTERNAL);
+							foreach(l, depRelOids)
+							{
+								Oid		depRelOid;
+								Oid		nspOid;
+								depRelOid = lfirst_oid(l);
+								nspOid = get_rel_namespace(depRelOid);
+								if (get_rel_relkind(depRelOid) == RELKIND_INDEX)
+								{
+									ereport(NOTICE,
+											(errmsg("ALTER TABLE / CONSTRAINT will implicitly rename index "
+													"\"%s\" to \"%s\" on table \"%s.%s\"",
+												get_rel_name(depRelOid),
+												stmt->newname,
+												get_namespace_name(nspOid),
+												get_rel_name(relid))));
+									renamerel(depRelOid, stmt->newname);
+								}
+							}
+						}
+						break;
+
 					default:
 						 /* can't happen */ ;
 				}

src/backend/parser/gram.y

@@ -11,7 +11,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/parser/gram.y,v 2.526 2006/02/04 19:06:46 adunstan Exp $
+ *	  $PostgreSQL: pgsql/src/backend/parser/gram.y,v 2.527 2006/02/11 22:17:18 momjian Exp $
  *
  * HISTORY
  *	  AUTHOR			DATE			MAJOR EVENT
@@ -4096,6 +4096,15 @@ RenameStmt: ALTER AGGREGATE func_name '(' aggr_argtype ')' RENAME TO name
 					n->newname = $8;
 					$$ = (Node *)n;
 				}
+			| ALTER TABLE relation_expr ALTER CONSTRAINT name RENAME TO name
+				{
+					RenameStmt *n = makeNode(RenameStmt);
+					n->renameType = OBJECT_CONSTRAINT;
+					n->relation = $3;
+					n->subname = $6;
+					n->newname = $9;
+					$$ = (Node *)n;
+				}
 			| ALTER TRIGGER name ON relation_expr RENAME TO name
 				{
 					RenameStmt *n = makeNode(RenameStmt);

src/backend/tcop/utility.c

@@ -10,7 +10,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/tcop/utility.c,v 1.250 2005/11/29 01:25:49 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/tcop/utility.c,v 1.251 2006/02/11 22:17:19 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1406,6 +1406,7 @@ CreateCommandTag(Node *parsetree)
 				case OBJECT_SCHEMA:
 					tag = "ALTER SCHEMA";
 					break;
+				case OBJECT_CONSTRAINT:
 				case OBJECT_COLUMN:
 				case OBJECT_TABLE:
 					tag = "ALTER TABLE";