From: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Samuel Sieb <samuel(at)sieb(dot)net>, Jan Wieck <JanWieck(at)Yahoo(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Performance monitor signal handler |
Date: | 2001-03-17 20:10:05 |
Message-ID: | 200103172010.PAA06443@candle.pha.pa.us |
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Thread: | |
Lists: | pgsql-hackers |
> > But per-table stats aren't something that people will look at often,
> > right? They can sit in the collector's memory for quite a while. See
> > people wanting to look at per-backend stuff frequently, and that is why
> > I thought share memory should be good, and a global area for aggregate
> > stats for all backends.
>
> >> I think you missed the point that somebody made a little while ago
> >> about waiting for functions that can return tuple sets. Once we have
> >> that, the stats tables can be *virtual* tables, ie tables that are
> >> computed on-demand by some function. That will be a lot less overhead
> >> than physically updating an actual table.
>
> > Yes, but do we want to keep these stats between postmaster restarts?
> > And what about writing them to tables when our storage of table stats
> > gets too big?
>
> All those points seem to me to be arguments in *favor* of a virtual-
> table approach, not arguments against it.
>
> Or are you confusing the method of collecting stats with the method
> of making the collected stats available for use?
Maybe I am confusing them. I didn't see a distinction in the
discussion.
I assumed the UDP/message passing of information to the collector was
the way statistics were collected, and I don't understand why a
per-backend area and global area, with some kind of cicular buffer for
per-table stuff isn't the cheapest, cleanest solution.
--
Bruce Momjian | http://candle.pha.pa.us
pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 853-3000
+ If your life is a hard drive, | 830 Blythe Avenue
+ Christ can be your backup. | Drexel Hill, Pennsylvania 19026
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