From: | Philip Molter <philip(at)datafoundry(dot)net> |
---|---|
To: | Richard Huxton <dev(at)archonet(dot)com> |
Cc: | Sam Tregar <sam(at)tregar(dot)com>, pgsql-general(at)postgresql(dot)org |
Subject: | Re: Determining scan types |
Date: | 2001-07-03 17:18:32 |
Message-ID: | 20010703121831.V12723@datafoundry.net |
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Lists: | pgsql-general |
On Tue, Jul 03, 2001 at 05:12:43PM +0100, Richard Huxton wrote:
: VACUUM ANALYZE frequency depends on numbers of updates. I believe someone
: has been looking at a way of doing this in the background.
Oh yeah, definitely depends on updates, or rather, changes to the
table contents (insertions, deletions).
: For the purposes of setting SEQSCAN try something like:
:
: SET ENABLE_SEQSCAN TO OFF;
:
: Can't remember if it applies to this transaction or this connection. Run a
: grep on the docs - you'll only find a couple of hits.
Well, I turned it off for the entire database (since right now, we're
only using the db for this one application), but I lose the benefit of
seqscans in situations where it's appropriate. That's why I was
wondering if there's anyway to tell the optimizer to prefer index scans
over sequential scans when it has a choice. Right now, it's using less
efficient joining methods where it would normally use sequential scans
(not that I'm complaining too much; CPU performance has more than
doubled since taking out sequential scans).
* Philip Molter
* DataFoundry.net
* http://www.datafoundry.net/
* philip(at)datafoundry(dot)net
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