Re: current_query in pg_stat_activity

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

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