Re: GiST index performance

From: Craig Ringer <craig(at)postnewspapers(dot)com(dot)au>
To: dforum <dforums(at)vieonet(dot)com>
Cc: Matthew Wakeling <matthew(at)flymine(dot)org>, pgsql-performance(at)postgresql(dot)org
Subject: Re: GiST index performance
Date: 2009-04-17 01:22:08
Message-ID: 49E7D9C0.90901@postnewspapers.com.au
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dforum wrote:
> hello,
>
> there is other performance problem on this request.
>
> If you analyse query plan, you see that most of the time are lost during
> sequencial scan, and you have 2 seq scan.
>
> You have to create other indexes to match the request.
>
> Postgresq is totally dependant on index to reach is performance.

That depends a lot on your queries. Sometimes a sequential scan is a
faster and better choice. It may also be faster for small tables.

I've usually found that when I (for performance testing purposes) force
the planner to an index scan instead of its preferred sequential scan,
the query runs slower than it did with a sequential scan.

Sure, there are queries that are horrifyingly slow without appropriate
indexes, but I wouldn't go so far as to say that Pg is totally dependent
on indexes to perform well. It depends a lot on the query.

--
Craig Ringer

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