CREATE TEMPORARY TABLE t1 (i INT, t TEXT) USING memoryam;
INSERT INTO t1 VALUES (1, 'hello');
-- should be one entry
SELECT * FROM t1;
 i |   t   
---+-------
 1 | hello
(1 row)

BEGIN;
INSERT into t1 VALUES (2, 'world');
-- should be two entries
SELECT * FROM t1;
 i |   t   
---+-------
 1 | hello
 2 | world
(2 rows)

ROLLBACK;
-- should be back to one entry
SELECT * FROM t1;
 i |   t   
---+-------
 1 | hello
(1 row)

BEGIN;
-- should be two entries
INSERT INTO t1 VALUES (2, 'world');
SELECT * FROM t1;
 i |   t   
---+-------
 1 | hello
 2 | world
(2 rows)

COMMIT;
-- should still be two entries
SELECT * FROM t1;
 i |   t   
---+-------
 1 | hello
 2 | world
(2 rows)

BEGIN;
DELETE FROM t1 WHERE i = 2;
-- should be one entry
SELECT * FROM t1;
 i |   t   
---+-------
 1 | hello
(1 row)

ROLLBACK;
-- should be back to two entries
SELECT * FROM t1;
 i |   t   
---+-------
 1 | hello
 2 | world
(2 rows)

BEGIN;
DELETE FROM t1;
-- should be no entries
SELECT * FROM t1;
 i | t 
---+---
(0 rows)

COMMIT;
-- should still be no entries
SELECT * FROM t1;
 i | t 
---+---
(0 rows)

DROP TABLE t1;