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Re: pg_upgrade and statistics

From: "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
To: "Daniel Farina" <daniel(at)heroku(dot)com>,"Greg Stark" <stark(at)mit(dot)edu>
Cc: "pgsql-hackers" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: pg_upgrade and statistics
Date: 2012-03-13 18:18:58
Message-ID: 4F5F4942020000250004622E@gw.wicourts.gov (view raw or flat)
Thread:
Lists: pgsql-hackers
Greg Stark <stark(at)mit(dot)edu> wrote:
> Daniel Farina <daniel(at)heroku(dot)com> wrote:
>> You probably are going to ask: "why not just run ANALYZE and be
>> done with it?"
> 
> Uhm yes. If analyze takes a long time then something is broken.
> It's only reading a sample which should be pretty much a fixed
> number of pages per table. It shouldn't take much longer on your
> large database than on your smaller databases.
 
On a small database:
 
cc=# analyze "CaseHist";
ANALYZE
Time: 255.107 ms
cc=# select relpages, reltuples from pg_class where relname =
'CaseHist';
 relpages | reltuples 
----------+-----------
     1264 |     94426
(1 row)
 
Same table on a much larger database (and much more powerful
hardware):
 
cir=# analyze "CaseHist";
ANALYZE
Time: 143450.467 ms
cir=# select relpages, reltuples from pg_class where relname =
'CaseHist';
 relpages |  reltuples  
----------+-------------
  3588659 | 2.12391e+08
(1 row)
 
Either way, there are about 500 tables in the database.
 
-Kevin

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