Re: Where does data in pg_stat_user_tables come from?

Le 16/09/2010 20:39, Josh Berkus a écrit :
>
>> It's been pure nonsense in this thread.  Please show an example of
>> what's not working.
>
> 1) Init a postgresql 8.3 with autovacuum disabled.
>
> 2) Load a backup of a database into that PostgreSQL.
>
> 3) Check pg_stat_user_tables.  n_live_tup for all tables will be 0.
>
> 4) VACUUM ANALYZE the whole database.
>
> 5) n_live_tup will *still* be 0.  Whereas reltuples in pg_class will be
> reasonable accurate.
>

Did all your steps (except the fourth one). Works great (meaning
n_live_tup is updated as it should be).

I have to agree with Alvarro, this is complete nonsense. VACUUM ANALYZE
doesn't change the pg_stat_*_tables columns value, the stats collector does.

If your n_live_tup didn't get updated, I'm quite sure you have
track_counts to off in your postgresql.conf file.

>> Um ... it updates the last_autovacuum and last_autoanalyze columns,
>> but the others are not its responsibility.
>
> Right. I'm contending that ANALYZE *should* update those columns.

The postgres process executing ANALYZE surely sent this information to
the stats collector (once again, if track_counts is on). Tried it
tonight, works great too.

> Current behavior is unintuitive and makes the stats in
> pg_stat_user_tables almost useless, since you can never get even
> approximately a coherent snapshot of data for all tables.
>

Get a look at your track_count setting.


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Guillaume
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