mvcctest=# INSERT INTO mvcc_demo VALUES (1);VACUUM mvcc_demo;SELECT pg_freespace('mvcc_demo');
INSERT 0 1
VACUUM
 pg_freespace 
--------------
 (0,8128)
(1 row)

mvcctest=# INSERT INTO mvcc_demo VALUES (2);VACUUM mvcc_demo;SELECT pg_freespace('mvcc_demo');
INSERT 0 1
VACUUM
 pg_freespace 
--------------
 (0,8064)
(1 row)

mvcctest=# INSERT INTO mvcc_demo VALUES (3);VACUUM mvcc_demo;SELECT pg_freespace('mvcc_demo');
INSERT 0 1
VACUUM
 pg_freespace 
--------------
 (0,8032)
(1 row)

=# DELETE FROM mvcc_demo WHERE val = 3;VACUUM mvcc_demo;SELECT pg_freespace('mvcc_demo');
DELETE 1
VACUUM
 pg_freespace 
--------------
 (0,8064)
(1 row)

mvcctest=# DELETE FROM mvcc_demo WHERE val = 2;VACUUM mvcc_demo;SELECT pg_freespace('mvcc_demo');
DELETE 1
VACUUM
 pg_freespace 
--------------
 (0,8096)
(1 row)

mvcctest=# DELETE FROM mvcc_demo WHERE val = 1;VACUUM mvcc_demo;SELECT pg_freespace('mvcc_demo');
DELETE 1
VACUUM
 pg_freespace 
--------------
(0 rows)