200 RECORDS

count_test=# SELECT COUNT(*) FROM posts;
 count
-------
   200
(1 row)

Time: 2.756 ms

count_test=# SELECT COUNT(*) FROM posts WHERE topic = 1;
 count
-------
    18
(1 row)

Time: 0.552 ms

count_test=# SELECT post_count FROM topics WHERE id = 1;
 post_count
------------
         18
(1 row)

Time: 0.727 ms




LOTS OF RECORDS

count_test=# SELECT COUNT(*) FROM posts;
 count
--------
 267055
(1 row)

Time: 40.096 ms

count_test=# SELECT COUNT(*) FROM posts WHERE topic = 1;
 count
-------
 26929
(1 row)

Time: 58.331 ms

count_test=# SELECT post_count FROM topics WHERE id = 1;
 post_count
------------
(0 rows)

Time: 0.438 ms