Tighten ALTER FOREIGN TABLE .. SET DATA TYPE checks.

If the foreign table's rowtype is being used as the type of a column in
another table, we can't just up and change its data type.  This was
already checked for composite types and ordinary tables, but we
previously failed to enforce it for foreign tables.

Author: robertmhaas

src/backend/commands/tablecmds.c

@@ -3391,8 +3391,8 @@ ATRewriteTable(AlteredTableInfo *tab, Oid OIDNewHeap, LOCKMODE lockmode)
 	 */
 	if (newrel)
 		find_composite_type_dependencies(oldrel->rd_rel->reltype,
-										 RelationGetRelationName(oldrel),
-										 NULL);
+										 oldrel->rd_rel->relkind,
+										 RelationGetRelationName(oldrel));
 
 	/*
 	 * Generate the constraint and default execution states
@@ -3860,9 +3860,8 @@ ATTypedTableRecursion(List **wqueue, Relation rel, AlterTableCmd *cmd,
  * to reject the ALTER.  (How safe is this really?)
  */
 void
-find_composite_type_dependencies(Oid typeOid,
-								 const char *origTblName,
-								 const char *origTypeName)
+find_composite_type_dependencies(Oid typeOid, char origRelkind,
+								 const char *origRelname)
 {
 	Relation	depRel;
 	ScanKeyData key[2];
@@ -3905,20 +3904,19 @@ find_composite_type_dependencies(Oid typeOid,
 
 		if (rel->rd_rel->relkind == RELKIND_RELATION)
 		{
-			if (origTblName)
-				ereport(ERROR,
-						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-						 errmsg("cannot alter table \"%s\" because column \"%s\".\"%s\" uses its rowtype",
-								origTblName,
-								RelationGetRelationName(rel),
-								NameStr(att->attname))));
+			const char *msg;
+			if (origRelkind == RELKIND_COMPOSITE_TYPE)
+				msg = gettext_noop("cannot alter type \"%s\" because column \"%s\".\"%s\" uses it");
+			else if (origRelkind == RELKIND_FOREIGN_TABLE)
+				msg = gettext_noop("cannot alter foreign table \"%s\" because column \"%s\".\"%s\" uses its rowtype");
 			else
-				ereport(ERROR,
-						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-						 errmsg("cannot alter type \"%s\" because column \"%s\".\"%s\" uses it",
-								origTypeName,
-								RelationGetRelationName(rel),
-								NameStr(att->attname))));
+				msg = gettext_noop("cannot alter table \"%s\" because column \"%s\".\"%s\" uses its rowtype");
+			ereport(ERROR,
+					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+					 errmsg(msg,
+							origRelname,
+							RelationGetRelationName(rel),
+							NameStr(att->attname))));
 		}
 		else if (OidIsValid(rel->rd_rel->reltype))
 		{
@@ -3927,7 +3925,7 @@ find_composite_type_dependencies(Oid typeOid,
 			 * recursively check for indirect dependencies via its rowtype.
 			 */
 			find_composite_type_dependencies(rel->rd_rel->reltype,
-											 origTblName, origTypeName);
+											 origRelkind, origRelname);
 		}
 
 		relation_close(rel, AccessShareLock);
@@ -3943,7 +3941,7 @@ find_composite_type_dependencies(Oid typeOid,
 	 */
 	arrayOid = get_array_type(typeOid);
 	if (OidIsValid(arrayOid))
-		find_composite_type_dependencies(arrayOid, origTblName, origTypeName);
+		find_composite_type_dependencies(arrayOid, origRelkind, origRelname);
 }
 
 
@@ -6444,14 +6442,15 @@ ATPrepAlterColumnType(List **wqueue,
 					 errmsg("ALTER TYPE USING is not supported on foreign tables")));
 	}
 
-	if (tab->relkind == RELKIND_COMPOSITE_TYPE)
+	if (tab->relkind == RELKIND_COMPOSITE_TYPE
+		|| tab->relkind == RELKIND_FOREIGN_TABLE)
 	{
 		/*
 		 * For composite types, do this check now.  Tables will check
 		 * it later when the table is being rewritten.
 		 */
 		find_composite_type_dependencies(rel->rd_rel->reltype,
-										 NULL,
+										 rel->rd_rel->relkind,
 										 RelationGetRelationName(rel));
 	}
 

src/backend/commands/typecmds.c

@@ -2183,7 +2183,7 @@ get_rels_with_domain(Oid domainOid, LOCKMODE lockmode)
 			 */
 			if (OidIsValid(rel->rd_rel->reltype))
 				find_composite_type_dependencies(rel->rd_rel->reltype,
-												 NULL,
+												 RELKIND_COMPOSITE_TYPE,
 												 format_type_be(domainOid));
 
 			/* Otherwise we can ignore views, composite types, etc */

src/include/commands/tablecmds.h

@@ -53,8 +53,7 @@ extern void RenameRelationInternal(Oid myrelid,
 					   Oid namespaceId);
 
 extern void find_composite_type_dependencies(Oid typeOid,
-								 const char *origTblName,
-								 const char *origTypeName);
+								 char origRelkind, const char *origRelname);
 
 extern AttrNumber *varattnos_map(TupleDesc olddesc, TupleDesc newdesc);
 extern AttrNumber *varattnos_map_schema(TupleDesc old, List *schema);

src/test/regress/expected/foreign_data.out

@@ -692,7 +692,12 @@ ALTER FOREIGN TABLE ft1 ALTER COLUMN c8 TYPE char(10) using '0'; -- ERROR
 ERROR:  ALTER TYPE USING is not supported on foreign tables
 ALTER FOREIGN TABLE ft1 ALTER COLUMN c8 TYPE char(10);
 ALTER FOREIGN TABLE ft1 ALTER COLUMN c8 SET DATA TYPE text;
-ALTER FOREIGN TABLE ft1 ADD CONSTRAINT ft1_c9_check CHECK (c9 < 0);
+-- can't change the column type if it's used elsewhere
+CREATE TABLE use_ft1_column_type (x ft1);
+ALTER FOREIGN TABLE ft1 ALTER COLUMN c8 SET DATA TYPE integer;	-- ERROR
+ERROR:  cannot alter foreign table "ft1" because column "use_ft1_column_type"."x" uses its rowtype
+DROP TABLE use_ft1_column_type;
+ALTER FOREIGN TABLE ft1 ADD CONSTRAINT ft1_c9_check CHECK (c9 < 0); -- ERROR
 ERROR:  "ft1" is not a table
 ALTER FOREIGN TABLE ft1 DROP CONSTRAINT no_const;               -- ERROR
 ERROR:  "ft1" is not a table

src/test/regress/sql/foreign_data.sql

@@ -293,7 +293,11 @@ ALTER FOREIGN TABLE ft1 ALTER COLUMN c7 DROP NOT NULL;
 ALTER FOREIGN TABLE ft1 ALTER COLUMN c8 TYPE char(10) using '0'; -- ERROR
 ALTER FOREIGN TABLE ft1 ALTER COLUMN c8 TYPE char(10);
 ALTER FOREIGN TABLE ft1 ALTER COLUMN c8 SET DATA TYPE text;
-ALTER FOREIGN TABLE ft1 ADD CONSTRAINT ft1_c9_check CHECK (c9 < 0);
+-- can't change the column type if it's used elsewhere
+CREATE TABLE use_ft1_column_type (x ft1);
+ALTER FOREIGN TABLE ft1 ALTER COLUMN c8 SET DATA TYPE integer;	-- ERROR
+DROP TABLE use_ft1_column_type;
+ALTER FOREIGN TABLE ft1 ADD CONSTRAINT ft1_c9_check CHECK (c9 < 0); -- ERROR
 ALTER FOREIGN TABLE ft1 DROP CONSTRAINT no_const;               -- ERROR
 ALTER FOREIGN TABLE ft1 DROP CONSTRAINT IF EXISTS no_const;
 ALTER FOREIGN TABLE ft1 DROP CONSTRAINT ft1_c1_check;