Hi,
Which would be better to do, max() or select .. order by limit 1? Is 7.1
much better than 7.0.3 in doing the "limit 1"? I see that their EXPLAINs
are different - 7.1 has a limit cost.
(pid is a serial in the ep_posts table)
*** For Version 7.0.3
lylyeoh=# explain select max(pid) from ep_posts;
NOTICE: QUERY PLAN:
Aggregate (cost=8.50..8.50 rows=1 width=4)
-> Seq Scan on ep_posts (cost=0.00..8.00 rows=200 width=4)
EXPLAIN
lylyeoh=# explain select pid from ep_posts order by pid desc limit 1;
NOTICE: QUERY PLAN:
Index Scan Backward using ep_posts_pid_key on ep_posts (cost=0.00..26.20
rows=200 width=4)
EXPLAIN
*** For version 7.1beta4
explain select max(pid) from ep_posts;
NOTICE: QUERY PLAN:
Aggregate (cost=8.50..8.50 rows=1 width=4)
-> Seq Scan on ep_posts (cost=0.00..8.00 rows=200 width=4)
EXPLAIN
lylyeoh=> explain select pid from ep_posts order by pid desc limit 1;
NOTICE: QUERY PLAN:
Limit (cost=0.00..0.13 rows=1 width=4)
-> Index Scan Backward using ep_posts_pid_key on ep_posts
(cost=0.00..26.20 rows=200 width=4)
EXPLAIN
