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Re: pg_upgrade and statistics

From: Bruce Momjian <bruce(at)momjian(dot)us>
To: Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>
Cc: Daniel Farina <daniel(at)heroku(dot)com>, Greg Stark <stark(at)mit(dot)edu>,pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: pg_upgrade and statistics
Date: 2012-03-13 18:53:26
Message-ID: 20120313185326.GB23967@momjian.us (view raw or flat)
Thread:
Lists: pgsql-hackers
On Tue, Mar 13, 2012 at 01:18:58PM -0500, Kevin Grittner wrote:
> 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.

That is 2.5 minutes.  How large is that database?

-- 
  Bruce Momjian  <bruce(at)momjian(dot)us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

  + It's impossible for everything to be true. +

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