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

From: "Dolafi, Tom" <dolafit(at)janelia(dot)hhmi(dot)org>
To: "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: <pgsql-performance(at)postgresql(dot)org>
Subject: Re: rtree/gist index taking enormous amount of space in 8.2.3
Date: 2007-06-29 13:51:19
Message-ID: AE9860225100F14D87B26D0D4D6766DB46F3E7@EXCHANGE03.janelia.priv (view raw or flat)
Thread:
Lists: pgsql-performance
min(fmin) |   max(fmin)    |    avg(fmin)      
   1      |   55296469     |    11423945     

min(fmax) |   max(fmax)    |    avg(fmax)
  18      |   55553288     |    11424491

There are 5,704,211 rows in the table.

This application has been inherited by us.  As far as I can tell the
magic of the two constants seem to represent the notion of infinity.

Thanks,
Tom

-----Original Message-----
From: Tom Lane [mailto:tgl(at)sss(dot)pgh(dot)pa(dot)us] 
Sent: Thursday, June 28, 2007 12:09 PM
To: Dolafi, Tom
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: [PERFORM] rtree/gist index taking enormous amount of space
in 8.2.3 

"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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