Re: Better estimates of index correlation - Mailing list pgsql-hackers

From Jeff Davis
Subject Re: Better estimates of index correlation
Date
Msg-id 1300235521.3102.2.camel@jdavis-ux.asterdata.local
Whole thread Raw
In response to Better estimates of index correlation  (Tom Lane <tgl@sss.pgh.pa.us>)
List pgsql-hackers
On Sun, 2011-03-13 at 19:40 -0400, Tom Lane wrote:
> It strikes me that it'd be possible to have btvacuumcleanup directly
> measure order correlation when it's processing a btree index, yielding a
> reliable answer for any btree index regardless of number of columns.
> We could do that by comparing the heap block numbers of adjacent
> index entries' TIDs and counting the number of up-transitions (block
> number larger than previous index entry) versus down-transitions (block
> number smaller than previous). 

Link to previous discussion:

http://archives.postgresql.org/pgsql-hackers/2008-10/msg01279.php

Regards,Jeff Davis



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