Re: current_query in pg_stat_activity

From: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
To: Jan Wieck <JanWieck(at)Yahoo(dot)com>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Oliver Fromme <olli(at)lurza(dot)secnetix(dot)de>, pgsql-novice(at)postgresql(dot)org
Subject: Re: current_query in pg_stat_activity
Date: 2004-03-02 16:34:57
Message-ID: 200403021634.i22GYwG19307@candle.pha.pa.us
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Attached patch applied. Thanks for the analysis.

---------------------------------------------------------------------------

Jan Wieck wrote:
> Tom Lane wrote:
> > Oliver Fromme <olli(at)lurza(dot)secnetix(dot)de> writes:
> >> Tom Lane wrote:
> >>>> Oliver Fromme <olli(at)lurza(dot)secnetix(dot)de> writes:
> >>>>> The "current_query" column in the "pg_stat_activity" system
> >>>>> table seems to be limited to 255 characters. Is there a way
> >>>>> to increase that limit, in order to see queries completely
> >>>>> which are longer than 255 characters?
> >>>>
> >>>> You could fool with PGSTAT_ACTIVITY_SIZE in pgstat.h, but you probably
> >>>> need to keep it under 1000 --- note the comments associated with
> >>>> PGSTAT_NUM_TABENTRIES.
> >
> >> Thanks! It appears that the size is ultimately limited
> >> by the MTU of the localhost interface, which is 16K on
> >> my platform (FreeBSD), so I should be able to increase
> >> PGSTAT_ACTIVITY_SIZE to something like 15K, right?
> >
> > You'll probably find the overhead of the stats collector ballooning
> > quite a lot if you increase the max message size by a factor of 15 :-(.
> > But give it a try.
> >
> >> Oh, by the way, while I'm at it, I think I found a small
> >> bug in the second of those formulas (PostgreSQL 7.3.5):
> >
> >> #define PGSTAT_NUM_TABPURGE ((1000 - sizeof(PgStat_MsgHdr)) \
> >> / sizeof(PgStat_TableEntry))
> >
> >> That should be sizeof(Oid), shouldn't it? The bug doesn't
> >> hurt because a Oid is much smaller than a PgStat_TableEntry,
> >> but it limits the number of them inside a PgStat_MsgTabpurge
> >> much more than necessary.
> >
> > I think you are right. Jan?
>
> Looks very much like, as the payload of the purge message is just an
> array of oids.
>
>
> Jan
>
> --
> #======================================================================#
> # It's easier to get forgiveness for being wrong than for being right. #
> # Let's break this rule - forgive me. #
> #================================================== JanWieck(at)Yahoo(dot)com #
>
>
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--
Bruce Momjian | http://candle.pha.pa.us
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