From: | Magnus Hagander <magnus(at)hagander(dot)net> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Greg Smith <greg(at)2ndquadrant(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: More vacuum stats |
Date: | 2010-08-23 14:40:46 |
Message-ID: | AANLkTimi2YWt-Xa4LjxiCPLBN_k4u4=KjQwAft9eysjd@mail.gmail.com |
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Lists: | pgsql-hackers |
On Mon, Aug 23, 2010 at 16:38, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Magnus Hagander <magnus(at)hagander(dot)net> writes:
>> On Mon, Aug 23, 2010 at 16:28, Greg Smith <greg(at)2ndquadrant(dot)com> wrote:
>>> What I actually want here is for the time that the last table autovacuum
>>> started, adding to the finish time currently exposed by pg_stat_user_tables.
>
>> Now, that would be quite useful. That'd require another stats message,
>> since we don't send anything on autovacuum start, but I don't think
>> the overhead of that is anything we need to worry about - in
>> comparison to an actual vacuum...
>
> No, you wouldn't really need an extra message, you could just send both
> start and finish times in the completion message. I'm not sure that
> having last start time update before last end time would be a good idea
> anyway.
Hmm, good point. We'd just need an extra field in that message.
> But in any case it's true that an extra message wouldn't be a
> significant cost. What I'd be more concerned about is the stats table
> bloat from adding yet another per-table field. That could be a lot of
> space on an installation with lots of tables.
>
>> We could also store last_autovacuum_vacuum_duration - is that better
>> or worse than start and end time?
>
> No, I think you want to know the actual time not only the duration.
Well, you could calculate one from the other - especially if one takes
less size, per your comment above.
--
Magnus Hagander
Me: http://www.hagander.net/
Work: http://www.redpill-linpro.com/
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