Re: Autovacuum daemon functionality questions

Gnanakumar wrote:

> 1. Why need to have 2 parameters (base threshold and scale factor) to define
> the threshold value, when either one of the parameter is more than enough to
> define the threshold value.  Can you explain the significance of having both
> parameters.  What is the real-time advantage of this?

real-time advantage?  They are just the two factors in a linear
equation.

> 2. Documentation says ".... If the number of obsolete tuples since the last
> VACUUM exceeds the "vacuum threshold", the table is vacuumed ...".
> I also know about this table "pg_stat_user_tables" which has columns
> n_tup_ins, n_tup_upd, n_tup_del, last_autovaccum and last_autoanalyze.
> Since INSERT, UPDATE and DELETE count gets incremented everytime and do not
> reset after running autovacuum/autoanalyze, how does autovacuum identifies
> obsolete tuples since last VACUUM from this entries.

There are two separate counters for live and dead tuples, IIRC (though
they may not be exposed in the pg_stat views)

> 3. Is there a way to see autovacuum daemon log entries?

Not in 8.2.

--
Alvaro Herrera                                http://www.CommandPrompt.com/
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