SELECT pgperf.create_snapshot_pg_database_size(0);
 create_snapshot_pg_database_size 
----------------------------------
 t
(1 row)

SELECT pgperf.create_snapshot_pg_database_size(1);
 create_snapshot_pg_database_size 
----------------------------------
 t
(1 row)

SELECT count(*) FROM pgperf.snapshot_pg_database_size;
 count 
-------
     2
(1 row)

SELECT pgperf.delete_snapshot_pg_database_size(1);
 delete_snapshot_pg_database_size 
----------------------------------
 t
(1 row)

SELECT count(*) FROM pgperf.snapshot_pg_database_size;
 count 
-------
     1
(1 row)

SELECT pgperf.delete_snapshot_pg_database_size(0);
 delete_snapshot_pg_database_size 
----------------------------------
 t
(1 row)

SELECT count(*) FROM pgperf.snapshot_pg_database_size;
 count 
-------
     0
(1 row)