From 6e2a6bdfb77870213d051f31b2b6683ccea45ab2 Mon Sep 17 00:00:00 2001
From: Himanshu Upadhyaya <himanshu.upadhyaya@enterprisedb.com>
Date: Mon, 5 Apr 2021 21:04:56 +0530
Subject: [PATCH v1] PREPARE TRANSACTION must fail when mixed with temporary
 object.

---
 src/backend/utils/cache/typcache.c | 30 ++++++++++++++++--------------
 src/test/regress/expected/temp.out | 14 ++++++++++++++
 src/test/regress/sql/temp.sql      | 14 ++++++++++++++
 3 files changed, 44 insertions(+), 14 deletions(-)

diff --git a/src/backend/utils/cache/typcache.c b/src/backend/utils/cache/typcache.c
index 4915ef5934..36fac6150d 100644
--- a/src/backend/utils/cache/typcache.c
+++ b/src/backend/utils/cache/typcache.c
@@ -813,7 +813,6 @@ lookup_type_cache(Oid type_id, int flags)
 	 * If it's a composite type (row type), get tupdesc if requested
 	 */
 	if ((flags & TYPECACHE_TUPDESC) &&
-		typentry->tupDesc == NULL &&
 		typentry->typtype == TYPTYPE_COMPOSITE)
 	{
 		load_typcache_tupdesc(typentry);
@@ -881,21 +880,25 @@ load_typcache_tupdesc(TypeCacheEntry *typentry)
 
 	/*
 	 * Link to the tupdesc and increment its refcount (we assert it's a
-	 * refcounted descriptor).  We don't use IncrTupleDescRefCount() for this,
-	 * because the reference mustn't be entered in the current resource owner;
+	 * refcounted descriptor), do this only if it was not populated previously.
+	 * We don't use IncrTupleDescRefCount() for this, because the reference
+	 * mustn't be entered in the current resource owner;
 	 * it can outlive the current query.
 	 */
-	typentry->tupDesc = RelationGetDescr(rel);
+	if (typentry->tupDesc == NULL)
+	{
+		typentry->tupDesc = RelationGetDescr(rel);
 
-	Assert(typentry->tupDesc->tdrefcount > 0);
-	typentry->tupDesc->tdrefcount++;
+		Assert(typentry->tupDesc->tdrefcount > 0);
+		typentry->tupDesc->tdrefcount++;
 
-	/*
-	 * In future, we could take some pains to not change tupDesc_identifier if
-	 * the tupdesc didn't really change; but for now it's not worth it.
-	 */
-	typentry->tupDesc_identifier = ++tupledesc_id_counter;
+		/*
+		 * In future, we could take some pains to not change tupDesc_identifier if
+		 * the tupdesc didn't really change; but for now it's not worth it.
+		 */
+		typentry->tupDesc_identifier = ++tupledesc_id_counter;
 
+	}
 	relation_close(rel, AccessShareLock);
 }
 
@@ -1529,9 +1532,8 @@ cache_record_field_properties(TypeCacheEntry *typentry)
 		int			newflags;
 		int			i;
 
-		/* Fetch composite type's tupdesc if we don't have it already */
-		if (typentry->tupDesc == NULL)
-			load_typcache_tupdesc(typentry);
+		/* Fetch composite type's tupdesc */
+		load_typcache_tupdesc(typentry);
 		tupdesc = typentry->tupDesc;
 
 		/* Must bump the refcount while we do additional catalog lookups */
diff --git a/src/test/regress/expected/temp.out b/src/test/regress/expected/temp.out
index a5b3ed34a3..ebf5909389 100644
--- a/src/test/regress/expected/temp.out
+++ b/src/test/regress/expected/temp.out
@@ -319,6 +319,20 @@ select relname from pg_class where relname ~ '^temp_inh_oncommit_test';
 (1 row)
 
 drop table temp_inh_oncommit_test;
+-- Test for accessing Temporary table
+-- in prepare transaction.
+-- These cases must fail and generate errors about Temporary objects.
+CREATE TEMP TABLE temp_tbl (first TEXT, last TEXT);
+BEGIN;
+CREATE FUNCTION longname(temp_tbl) RETURNS TEXT LANGUAGE SQL
+AS $$SELECT $1.first || ' ' || $1.last$$;
+PREPARE TRANSACTION 'temp_tbl_access';
+ERROR:  cannot PREPARE a transaction that has operated on temporary objects
+BEGIN;
+CREATE FUNCTION longname(temp_tbl) RETURNS TEXT LANGUAGE SQL
+AS $$SELECT $1.first || ' ' || $1.last$$;
+PREPARE TRANSACTION 'temp_tbl_access';
+ERROR:  cannot PREPARE a transaction that has operated on temporary objects
 -- Tests with two-phase commit
 -- Transactions creating objects in a temporary namespace cannot be used
 -- with two-phase commit.
diff --git a/src/test/regress/sql/temp.sql b/src/test/regress/sql/temp.sql
index 424d12b283..7cda474782 100644
--- a/src/test/regress/sql/temp.sql
+++ b/src/test/regress/sql/temp.sql
@@ -240,6 +240,20 @@ select * from temp_inh_oncommit_test;
 select relname from pg_class where relname ~ '^temp_inh_oncommit_test';
 drop table temp_inh_oncommit_test;
 
+-- Test for accessing Temporary table
+-- in prepare transaction.
+-- These cases must fail and generate errors about Temporary objects.
+CREATE TEMP TABLE temp_tbl (first TEXT, last TEXT);
+BEGIN;
+CREATE FUNCTION longname(temp_tbl) RETURNS TEXT LANGUAGE SQL
+AS $$SELECT $1.first || ' ' || $1.last$$;
+PREPARE TRANSACTION 'temp_tbl_access';
+
+BEGIN;
+CREATE FUNCTION longname(temp_tbl) RETURNS TEXT LANGUAGE SQL
+AS $$SELECT $1.first || ' ' || $1.last$$;
+PREPARE TRANSACTION 'temp_tbl_access';
+
 -- Tests with two-phase commit
 -- Transactions creating objects in a temporary namespace cannot be used
 -- with two-phase commit.
-- 
2.25.1