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Re: GiST index performance

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
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: 2009-04-16 17:52:35
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-performance
dforum <dforums(at)vieonet(dot)com> writes:
> If you analyse query plan, you see that most of the time are lost during 
> sequencial scan, and you have 2 seq scan.

I think you missed the loops count.

>>          ->  Index Scan using location_object_start_gist on location l1
>>                (cost=0.00..4.16 rows=150 width=65)
>>                (actual time=3.354..10.757 rows=3 loops=211880)
>>                Index Cond: ((l1.objectid = l2.objectid) AND 
>> (l2.intermine_start <= l1.intermine_start) AND (l2.intermine_end >= 
>> l1.intermine_start))

This indexscan is accounting for 10.757 * 211880 msec, which is 99%
of the runtime.

			regards, tom lane

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