| From: | Christopher Kings-Lynne <chriskl(at)familyhealth(dot)com(dot)au> |
|---|---|
| To: | Jeff <threshar(at)torgo(dot)978(dot)org> |
| Cc: | Christopher Browne <cbbrowne(at)acm(dot)org>, "pgsql-performance(at)postgresql(dot)org" <pgsql-performance(at)postgresql(dot)org> |
| Subject: | Re: count(*) slow on large tables |
| Date: | 2003-10-04 09:37:32 |
| Message-ID: | 3F7E94DC.9090709@familyhealth.com.au |
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| Thread: | |
| Lists: | pgsql-hackers pgsql-performance |
> On our message boards each post is a row. The powers that be like to know
> how many posts there are total (In addition to 'today')-
> select count(*) from posts is how it has been
> done on our informix db. With our port to PG I instead select reltuples
> pg_class.
We have exactly the same situation, except we just added a 'num_replies'
field to each thread and a 'num_posts' field to each forum, so that
getting that information out is a very fast operation. Because, of
course, there are hundreds of times more reads of that information than
writes...
Chris
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