Re: current_query in pg_stat_activity

Tom Lane wrote:
 > Oliver Fromme <olli@lurza.secnetix.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?

I'll also have to adjust the numbers in the calculations
of PGSTAT_NUM_TABENTRIES and PGSTAT_NUM_TABPURGE from
1000 to (say) 16000, of course.

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 haven't looked at 7.4.1; maybe it's already fixed.)

Best regards
   Oliver

--
Oliver Fromme, secnetix GmbH & Co KG, Oettingenstr. 2, 80538 München
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