Re: Select max(foo) and select count(*) optimization

On January 6, 2004 01:42 am, Shridhar Daithankar wrote:
> On Tuesday 06 January 2004 01:22, Rod Taylor wrote:
> > Anyway, with Rules you can force this:
> >
> > ON INSERT UPDATE counter SET tablecount = tablecount + 1;
> >
> > ON DELETE UPDATE counter SET tablecount = tablecount - 1;
>
> That would generate lot of dead tuples in counter table. How about
>
> select relpages,reltuples from pg_class where relname=<tablename>;
>
> Assuming the stats are recent enough, it would be much faster and
> accurate..

Well, I did this:

cert=# select relpages,reltuples from pg_class where relname= 'certificate';
relpages | reltuples
----------+-------------
399070 | 2.48587e+07
(1 row)

Casting seemed to help:

cert=# select relpages,reltuples::bigint from pg_class where relname=
'certificate';
relpages | reltuples
----------+-----------
399070 | 24858736
(1 row)

But:

cert=# select count(*) from certificate;
[*Crunch* *Crunch* *Crunch*]
count
----------
19684668
(1 row)

Am I missing something? Max certificate_id is 20569544 btw.

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