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Re: index usage

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "scott(dot)marlowe" <scott(dot)marlowe(at)ihs(dot)com>
Cc: Stephan Szabo <sszabo(at)megazone(dot)bigpanda(dot)com>,brad-pgperf(at)duttonbros(dot)com, pgsql-performance(at)postgresql(dot)org
Subject: Re: index usage
Date: 2004-04-28 16:41:40
Message-ID: 424.1083170500@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-performance
"scott.marlowe" <scott(dot)marlowe(at)ihs(dot)com> writes:
> There are tons of hints that it works this way in how they're written, but 
> nothing that just comes out and says that with pgsql's mvcc 
> implementation, an index scan still has to hit the pages that contain the 
> tuples, so often in pgsql a seq scan is a win where in other databases and 
> index scan would have been a win?

> If not, where would I add it if I were going to write something up for the 
> docs?  Just wondering...

AFAIR the only place in the docs that mentions seqscan or indexscan at
all is the discussion of EXPLAIN in "Performance Tips".  Perhaps a
suitably-enlarged version of that section could cover this.

			regards, tom lane

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