On 26.9.2012 18:29, Tom Lane wrote:
> What seems to me like it could help more is fixing things so that the
> autovac launcher needn't even launch a child process for databases that
> haven't had any updates lately.  I'm not sure how to do that, but it
> probably involves getting the stats collector to produce some kind of
> summary file.

Couldn't we use the PgStat_StatDBEntry for this? By splitting the
pgstat.stat file into multiple pieces (see my other post in this thread)
there's a file with StatDBEntry items only, so maybe it could be used as
the summary file ...

I've been thinking about this:

 (a) add "needs_autovacuuming" flag to PgStat_(TableEntry|StatDBEntry)

 (b) when table stats are updated, run quick check to decide whether
     the table needs to be processed by autovacuum (vacuumed or
     analyzed), and if yes then set needs_autovacuuming=true and both
     for table and database

The worker may read the DB entries from the file and act only on those
that need to be processed (those with needs_autovacuuming=true).

Maybe the DB-level field might be a counter of tables that need to be
processed, and the autovacuum daemon might act on those first? Although
the simpler the better I guess.

Or did you mean something else?


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