Re: pg_upgrade and statistics

On Tue, Mar 13, 2012 at 02:07:14PM -0500, Kevin Grittner wrote:
> Bruce Momjian <bruce(at)momjian(dot)us> wrote:
> > On Tue, Mar 13, 2012 at 01:18:58PM -0500, Kevin Grittner wrote:
>
> >> 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?
>
> cir=# select pg_size_pretty(pg_database_size('cir'));
> pg_size_pretty
> ----------------
> 2563 GB
> (1 row)
>
> In case you meant "How large is that table that took 2.5 minutes to
> analyze?":
>
> cir=# select pg_size_pretty(pg_total_relation_size('"CaseHist"'));
> pg_size_pretty
> ----------------
> 44 GB
> (1 row)
>
> I've started a database analyze, to see how long that takes. Even
> if each table took 1/4 second (like on the small database) with over
> 500 user tables, plus the system tables, it'd be 15 minutes. I'm
> guessing it'll run over an hour, but I haven't timed it lately, so
> -- we'll see.

OK, so a single 44GB tables took 2.5 minutes to analyze; that is not
good. It would require 11 such tables to reach 500GB (0.5 TB), and
would take 27 minutes. The report I had was twice as long, but still in
the ballpark of "too long". :-(

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

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