QUERY: SELECT count(*) FROM onek;
count
-----
 1000
(1 row)

QUERY: SELECT count(*) FROM onek where oidrand(onek.oid, 10);
count
-----
   92
(1 row)

QUERY: SELECT count(*) FROM onek where oidrand(onek.oid, 10);
count
-----
   98
(1 row)