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custom statistic collector

From: "Ilia Kantor" <ilia(at)obnovlenie(dot)ru>
To: <pgsql-hackers(at)postgresql(dot)org>
Subject: custom statistic collector
Date: 2005-08-29 21:18:21
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Lists: pgsql-hackers


I want to test my own selectivity function against future stats collector. 

Is this a right way to update statistic used by planner ?

update pg_statistic set
00,10001] where starelid=950855 and staattnum = 21;


stadistinct values total, stakind3 is my custom STATISTIC_KIND, stanumber3
are frequencies of stavalues3.



How to add custom statistic kind for 1-dim array of integers (_int4) ?

Currently it uses standard compute_scalar_stats (commands/analyze.c).


Custom statistic is needed to count selectivity for GIST built by

It should be gathered only for 1-dim arrays and contain most-common values
met in among all arrays,

Distinct values among all arrays etc.


Generally, it can be gathered on anyarray(not only _int4), but it's ok for
me (yet) to have it working for _int4 1-dim only.

Pitifully, I have no idea what is the right way of putting such thing into
existing system..


Should I add switches into analyze.c or there exist a better way ?


Maybe one could sketch out the structure of what is to be done. 






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