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Re: rtree/gist index taking enormous amount of space in 8.2.3

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "Dolafi, Tom" <dolafit(at)janelia(dot)hhmi(dot)org>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: rtree/gist index taking enormous amount of space in 8.2.3
Date: 2007-06-28 16:08:37
Message-ID: 13616.1183046917@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-performance
"Dolafi, Tom" <dolafit(at)janelia(dot)hhmi(dot)org> writes:
> In version 8.1.5, I have an rtree index on a 1.5 GB table.  The size of
> this index is 500 MB.  After migrating to 8.2.3, the size of this index
> has increased to 35GB.  I've dropped are recreated the index and got the
> same result.  In 8.2.3 the index type is gist, does this have something
> to do with it?

We dropped rtree in 8.2 on the strength of experiments that seemed to
show gist was always better, but you seem to have an outlier case...

Can you tell us something about the distribution of the data values
(fmin and fmax)?  Is there anything particularly magic about the two
constants you're using in the boxes?  I suppose you've hit some bad
corner case in the gist box opclass, but it's not clear what.

			regards, tom lane

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