| From: | Stephen Byers <stephenabyers(at)yahoo(dot)com> |
|---|---|
| To: | "Steinar H(dot) Gunderson" <sgunderson(at)bigfoot(dot)com>, pgsql-performance(at)postgresql(dot)org |
| Subject: | Re: why is bitmap index chosen for this query? |
| Date: | 2006-05-18 16:41:23 |
| Message-ID: | 20060518164123.98856.qmail@web30710.mail.mud.yahoo.com |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-performance |
"Steinar H. Gunderson" <sgunderson(at)bigfoot(dot)com> wrote:
It sounds like PostgreSQL badly overestimates the cost of the index scan.
Does the table perchance fit completely into memory, without
effective_cache_size indicating that?
Don't know the exact way to answer your question, but my initial instinct is "no way."
select pg_relation_size('packets');
pg_relation_size
------------------
19440115712
19GB. So it's a big table. The query I submitted earlier returns about 13M rows and the table currently has about 38M rows.
---------------------------------
Love cheap thrills? Enjoy PC-to-Phone calls to 30+ countries for just 2¢/min with Yahoo! Messenger with Voice.
| From | Date | Subject | |
|---|---|---|---|
| Next Message | Steinar H. Gunderson | 2006-05-18 16:46:40 | Re: why is bitmap index chosen for this query? |
| Previous Message | Ivan Zolotukhin | 2006-05-18 16:01:16 | Re: SQL CPU time usage |