Nested transactions. There is still much left to do, especially on the

performance front, but with feature freeze upon us I think it's time to
drive a stake in the ground and say that this will be in 7.5.

Alvaro Herrera, with some help from Tom Lane.

src/test/regress/expected/transactions.out

@@ -68,3 +68,70 @@ ERROR:  transaction is read-only
 START TRANSACTION READ WRITE;
 DROP TABLE writetest; -- ok
 COMMIT;
+-- Subtransactions, basic tests
+-- create & drop tables
+SET SESSION CHARACTERISTICS AS TRANSACTION READ WRITE;
+CREATE TABLE foobar (a int);
+BEGIN;
+	CREATE TABLE foo (a int);
+	BEGIN;
+		DROP TABLE foo;
+		CREATE TABLE bar (a int);
+	ROLLBACK;
+	BEGIN;
+		CREATE TABLE baz (a int);
+	COMMIT;
+	drop TABLE foobar;
+	CREATE TABLE barbaz (a int);
+COMMIT;
+-- should exist: barbaz, baz, foo
+SELECT * FROM foo;		-- should be empty
+ a 
+---
+(0 rows)
+
+SELECT * FROM bar;		-- shouldn't exist
+ERROR:  relation "bar" does not exist
+SELECT * FROM barbaz;	-- should be empty
+ a 
+---
+(0 rows)
+
+SELECT * FROM baz;		-- should be empty
+ a 
+---
+(0 rows)
+
+-- inserts
+BEGIN;
+	INSERT INTO foo VALUES (1);
+	BEGIN;
+		INSERT into bar VALUES (1);
+ERROR:  relation "bar" does not exist
+	ROLLBACK;
+	BEGIN;
+		INSERT into barbaz VALUES (1);
+	COMMIT;
+	BEGIN;
+		BEGIN;
+			INSERT INTO foo VALUES (2);
+		COMMIT;
+	ROLLBACK;
+	INSERT INTO foo VALUES (3);
+COMMIT;
+SELECT * FROM foo;		-- should have 1 and 3
+ a 
+---
+ 1
+ 3
+(2 rows)
+
+SELECT * FROM barbaz;	-- should have 1
+ a 
+---
+ 1
+(1 row)
+
+DROP TABLE foo;
+DROP TABLE baz;
+DROP TABLE barbaz;

src/test/regress/expected/without_oid.out

@@ -1,8 +1,18 @@
 --
 -- WITHOUT OID
 --
-CREATE TABLE wi (i INT) WITH OIDS;
-CREATE TABLE wo (i INT) WITHOUT OIDS;
+--
+-- This test tries to verify that WITHOUT OIDS actually saves space.
+-- On machines where MAXALIGN is 8, WITHOUT OIDS may or may not save any
+-- space, depending on the size of the tuple header + null bitmap.
+-- As of 7.5 we need a 9-bit null bitmap to force the difference to appear.
+--
+CREATE TABLE wi (i INT,
+                 n1 int, n2 int, n3 int, n4 int,
+                 n5 int, n6 int, n7 int, n8 int) WITH OIDS;
+CREATE TABLE wo (i INT,
+                 n1 int, n2 int, n3 int, n4 int,
+                 n5 int, n6 int, n7 int, n8 int) WITHOUT OIDS;
 INSERT INTO wi VALUES (1);  -- 1
 INSERT INTO wo SELECT i FROM wi;  -- 1
 INSERT INTO wo SELECT i+1 FROM wi;  -- 1+1=2
@@ -24,6 +34,15 @@ INSERT INTO wo SELECT i+896 FROM wi;  -- 896+2448=3344
 INSERT INTO wo SELECT i+3344 FROM wo;  -- 3344+3344=6688
 INSERT INTO wi SELECT i+2448 FROM wo;  -- 2448+6688=9136
 INSERT INTO wo SELECT i+6688 FROM wi WHERE i<=2448;  -- 6688+2448=9136
+SELECT count(oid) FROM wi;
+ count 
+-------
+  9136
+(1 row)
+
+-- should fail
+SELECT count(oid) FROM wo;
+ERROR:  column "oid" does not exist
 VACUUM ANALYZE wi;
 VACUUM ANALYZE wo;
 SELECT min(relpages) < max(relpages), min(reltuples) - max(reltuples)

src/test/regress/sql/transactions.sql

@@ -54,3 +54,48 @@ CREATE TABLE test AS SELECT * FROM writetest; -- fail
 START TRANSACTION READ WRITE;
 DROP TABLE writetest; -- ok
 COMMIT;
+
+-- Subtransactions, basic tests
+-- create & drop tables
+SET SESSION CHARACTERISTICS AS TRANSACTION READ WRITE;
+CREATE TABLE foobar (a int);
+BEGIN;
+	CREATE TABLE foo (a int);
+	BEGIN;
+		DROP TABLE foo;
+		CREATE TABLE bar (a int);
+	ROLLBACK;
+	BEGIN;
+		CREATE TABLE baz (a int);
+	COMMIT;
+	drop TABLE foobar;
+	CREATE TABLE barbaz (a int);
+COMMIT;
+-- should exist: barbaz, baz, foo
+SELECT * FROM foo;		-- should be empty
+SELECT * FROM bar;		-- shouldn't exist
+SELECT * FROM barbaz;	-- should be empty
+SELECT * FROM baz;		-- should be empty
+
+-- inserts
+BEGIN;
+	INSERT INTO foo VALUES (1);
+	BEGIN;
+		INSERT into bar VALUES (1);
+	ROLLBACK;
+	BEGIN;
+		INSERT into barbaz VALUES (1);
+	COMMIT;
+	BEGIN;
+		BEGIN;
+			INSERT INTO foo VALUES (2);
+		COMMIT;
+	ROLLBACK;
+	INSERT INTO foo VALUES (3);
+COMMIT;
+SELECT * FROM foo;		-- should have 1 and 3
+SELECT * FROM barbaz;	-- should have 1
+
+DROP TABLE foo;
+DROP TABLE baz;
+DROP TABLE barbaz;

src/test/regress/sql/without_oid.sql

@@ -2,8 +2,19 @@
 -- WITHOUT OID
 --
 
-CREATE TABLE wi (i INT) WITH OIDS;
-CREATE TABLE wo (i INT) WITHOUT OIDS;
+--
+-- This test tries to verify that WITHOUT OIDS actually saves space.
+-- On machines where MAXALIGN is 8, WITHOUT OIDS may or may not save any
+-- space, depending on the size of the tuple header + null bitmap.
+-- As of 7.5 we need a 9-bit null bitmap to force the difference to appear.
+--
+CREATE TABLE wi (i INT,
+                 n1 int, n2 int, n3 int, n4 int,
+                 n5 int, n6 int, n7 int, n8 int) WITH OIDS;
+CREATE TABLE wo (i INT,
+                 n1 int, n2 int, n3 int, n4 int,
+                 n5 int, n6 int, n7 int, n8 int) WITHOUT OIDS;
+
 INSERT INTO wi VALUES (1);  -- 1
 INSERT INTO wo SELECT i FROM wi;  -- 1
 INSERT INTO wo SELECT i+1 FROM wi;  -- 1+1=2
@@ -25,8 +36,14 @@ INSERT INTO wo SELECT i+896 FROM wi;  -- 896+2448=3344
 INSERT INTO wo SELECT i+3344 FROM wo;  -- 3344+3344=6688
 INSERT INTO wi SELECT i+2448 FROM wo;  -- 2448+6688=9136
 INSERT INTO wo SELECT i+6688 FROM wi WHERE i<=2448;  -- 6688+2448=9136
+
+SELECT count(oid) FROM wi;
+-- should fail
+SELECT count(oid) FROM wo;
+
 VACUUM ANALYZE wi;
 VACUUM ANALYZE wo;
+
 SELECT min(relpages) < max(relpages), min(reltuples) - max(reltuples)
   FROM pg_class
  WHERE relname IN ('wi', 'wo');