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

Joachim Wieland

Author: bmomjian

doc/src/sgml/ddl.sgml

@@ -1,4 +1,4 @@
-<!-- $PostgreSQL: pgsql/doc/src/sgml/ddl.sgml,v 1.52 2006/02/04 23:03:19 tgl Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/ddl.sgml,v 1.53 2006/02/11 22:17:18 momjian Exp $ -->
 
 <chapter id="ddl">
  <title>Data Definition</title>
@@ -543,6 +543,10 @@ CREATE TABLE products (
     price numeric
 );
 </programlisting>
+   Since <productname>PostgreSQL</productname> implements a UNIQUE constraint by
+   means of an index, the above command will also create an index with the same
+   name as the constraint. If you later on change the name of one of those, the
+   name of the corresponding object will be changed automatically as well.
    </para>
 
    <indexterm>

doc/src/sgml/ref/alter_index.sgml

@@ -1,5 +1,5 @@
 <!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/alter_index.sgml,v 1.6 2005/08/22 19:39:52 tgl Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/alter_index.sgml,v 1.7 2006/02/11 22:17:18 momjian Exp $
 PostgreSQL documentation
 -->
 
@@ -107,6 +107,15 @@ ALTER INDEX <replaceable class="PARAMETER">name</replaceable> SET TABLESPACE <re
     of <command>ALTER TABLE</> that apply to indexes.
    </para>
 
+   <para>
+    Indexes are also used internally by constraints, namely by UNIQUE and
+    PRIMARY KEY constraints. If you rename an index that is used internally by
+    a constraint of that type, this constraint will implicitly be renamed as
+    well. On the other hand, if you rename such a constraint, it will
+    implicitly rename its corresponding index such that both objects always
+    have the same name.
+   </para>
+
    <para>
     There was formerly an <command>ALTER INDEX OWNER</> variant, but
     this is now ignored (with a warning).  An index cannot have an owner

doc/src/sgml/ref/alter_table.sgml

@@ -1,5 +1,5 @@
 <!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/alter_table.sgml,v 1.82 2005/12/08 21:35:36 momjian Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/alter_table.sgml,v 1.83 2006/02/11 22:17:18 momjian Exp $
 PostgreSQL documentation
 -->
 
@@ -24,6 +24,8 @@ ALTER TABLE [ ONLY ] <replaceable class="PARAMETER">name</replaceable> [ * ]
     <replaceable class="PARAMETER">action</replaceable> [, ... ]
 ALTER TABLE [ ONLY ] <replaceable class="PARAMETER">name</replaceable> [ * ]
     RENAME [ COLUMN ] <replaceable class="PARAMETER">column</replaceable> TO <replaceable class="PARAMETER">new_column</replaceable>
+ALTER TABLE [ ONLY ] <replaceable class="PARAMETER">name</replaceable> [ * ]
+    ALTER CONSTRAINT <replaceable class="PARAMETER">constraint_name</replaceable> RENAME TO <replaceable class="PARAMETER">new_constraint_name</replaceable>
 ALTER TABLE <replaceable class="PARAMETER">name</replaceable>
     RENAME TO <replaceable class="PARAMETER">new_name</replaceable>
 ALTER TABLE <replaceable class="PARAMETER">name</replaceable>
@@ -169,6 +171,18 @@ where <replaceable class="PARAMETER">action</replaceable> is one of:
     </listitem>
    </varlistentry>
 
+   <varlistentry>
+    <term><literal>ALTER CONSTRAINT <replaceable class="PARAMETER">constraint_name</replaceable> RENAME TO <replaceable class="PARAMETER">new_constraint_name</replaceable></literal></term>
+    <listitem>
+     <para>
+      This form renames a constraint that is defined on the table. Note that if
+      a constraint is using an index internally (<literal>UNIQUE</> or
+      <literal>PRIMARY KEY</> constraints), the corresponding index will be
+      renamed as well.
+     </para>
+    </listitem>
+   </varlistentry>
+
    <varlistentry>
     <term><literal>ADD <replaceable class="PARAMETER">table_constraint</replaceable></literal></term>
     <listitem>

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;
+}
+