From 04db0fdbfa9382730bb65f94bca2cd8063a3456a Mon Sep 17 00:00:00 2001
From: Robert Haas <rhaas@postgresql.org>
Date: Mon, 18 Apr 2011 10:13:34 -0400
Subject: [PATCH] Only allow typed tables to hang off composite types, not e.g.
 tables.

This also ensures that we take a relation lock on the composite type when
creating a typed table, which is necessary to prevent the composite type
and the typed table from getting out of step in the face of concurrent
DDL.

Noah Misch, with some changes.
---
 src/backend/parser/parse_utilcmd.c        | 17 ++++++++++++++++-
 src/test/regress/expected/typed_table.out |  2 ++
 src/test/regress/sql/typed_table.sql      |  2 ++
 3 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/src/backend/parser/parse_utilcmd.c b/src/backend/parser/parse_utilcmd.c
index eba890bf88..4f1bb34dae 100644
--- a/src/backend/parser/parse_utilcmd.c
+++ b/src/backend/parser/parse_utilcmd.c
@@ -825,6 +825,7 @@ transformOfType(CreateStmtContext *cxt, TypeName *ofTypename)
 	TupleDesc	tupdesc;
 	int			i;
 	Oid			ofTypeId;
+	bool		typeOk = false;
 
 	AssertArg(ofTypename);
 
@@ -833,7 +834,21 @@ transformOfType(CreateStmtContext *cxt, TypeName *ofTypename)
 	ofTypeId = HeapTupleGetOid(tuple);
 	ofTypename->typeOid = ofTypeId;		/* cached for later */
 
-	if (typ->typtype != TYPTYPE_COMPOSITE)
+	if (typ->typtype == TYPTYPE_COMPOSITE)
+	{
+		Relation	typeRelation;
+
+		Assert(OidIsValid(typ->typrelid));
+		typeRelation = relation_open(typ->typrelid, AccessShareLock);
+		typeOk = (typeRelation->rd_rel->relkind == RELKIND_COMPOSITE_TYPE);
+		/*
+		 * Close the parent rel, but keep our AccessShareLock on it until xact
+		 * commit.	That will prevent someone else from deleting or ALTERing
+		 * the type before the typed table creation commits.
+		 */
+		relation_close(typeRelation, NoLock);
+	}
+	if (!typeOk)
 		ereport(ERROR,
 				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
 				 errmsg("type %s is not a composite type",
diff --git a/src/test/regress/expected/typed_table.out b/src/test/regress/expected/typed_table.out
index 0874a64d55..1fe426d6e3 100644
--- a/src/test/regress/expected/typed_table.out
+++ b/src/test/regress/expected/typed_table.out
@@ -91,6 +91,8 @@ DETAIL:  drop cascades to table persons
 drop cascades to function get_all_persons()
 drop cascades to table persons2
 drop cascades to table persons3
+CREATE TABLE persons5 OF stuff; -- only CREATE TYPE AS types may be used
+ERROR:  type stuff is not a composite type
 DROP TABLE stuff;
 -- implicit casting
 CREATE TYPE person_type AS (id int, name text);
diff --git a/src/test/regress/sql/typed_table.sql b/src/test/regress/sql/typed_table.sql
index b0d452c387..25aaccb8bc 100644
--- a/src/test/regress/sql/typed_table.sql
+++ b/src/test/regress/sql/typed_table.sql
@@ -46,6 +46,8 @@ CREATE TABLE persons4 OF person_type (
 DROP TYPE person_type RESTRICT;
 DROP TYPE person_type CASCADE;
 
+CREATE TABLE persons5 OF stuff; -- only CREATE TYPE AS types may be used
+
 DROP TABLE stuff;