| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Marc Boucher <pgml(at)gmx(dot)net> |
| Cc: | pgsql-general(at)postgresql(dot)org |
| Subject: | Re: index and queries using '<' '>' |
| Date: | 2004-11-19 15:22:32 |
| Message-ID: | 28011.1100877752@sss.pgh.pa.us |
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| Lists: | pgsql-general |
Marc Boucher <pgml(at)gmx(dot)net> writes:
>> Index scans aren't always faster than sequential scans.
> I know that, but I've some comparisons with other queries. And someone
> advised me to try "set enable_seqscan=off;". It takes 50-60% (after
> checking right now) less to use the index. Unfortunately I can't use this
> setting, the query being part of a larger query (joins), and the time
> gained on this particular index is partially lost on the joins.
A less brute-force way of encouraging the planner to use indexscans is
to reduce the random_page_cost setting. It defaults to 4 but many
people find that values nearer 2 are more representative of what happens
in their environments.
regards, tom lane
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