Thread: track_activity_query_size note
Hi, I attach a proposed change to the docs which points out that if the size of track_activity_query_size is changed and the is server restarted, it won't have any effect if query statistics are already present. Thanks Thom
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On Thu, May 24, 2012 at 2:16 PM, Thom Brown <thom@linux.com> wrote: > Hi, > > I attach a proposed change to the docs which points out that if the > size of track_activity_query_size is changed and the is server > restarted, it won't have any effect if query statistics are already > present. But aren't pg_stat_activity queries always cleared when you restart the server - because they are all disconnected... And you can't change track_activity_query_size without restarting. -- Magnus Hagander Me: http://www.hagander.net/ Work: http://www.redpill-linpro.com/
On 24 May 2012 13:39, Magnus Hagander <magnus@hagander.net> wrote: > On Thu, May 24, 2012 at 2:16 PM, Thom Brown <thom@linux.com> wrote: >> Hi, >> >> I attach a proposed change to the docs which points out that if the >> size of track_activity_query_size is changed and the is server >> restarted, it won't have any effect if query statistics are already >> present. > > But aren't pg_stat_activity queries always cleared when you restart > the server - because they are all disconnected... And you can't change > track_activity_query_size without restarting. But not pg_stat_statistics queries, which is where I should have probably made the note. Restarting the server won't change the length of the field if there's already data present in pg_stat_statistics, but upon resetting them, the field is appropriately sized. -- Thom
On Thu, May 24, 2012 at 2:49 PM, Thom Brown <thom@linux.com> wrote: > On 24 May 2012 13:39, Magnus Hagander <magnus@hagander.net> wrote: >> On Thu, May 24, 2012 at 2:16 PM, Thom Brown <thom@linux.com> wrote: >>> Hi, >>> >>> I attach a proposed change to the docs which points out that if the >>> size of track_activity_query_size is changed and the is server >>> restarted, it won't have any effect if query statistics are already >>> present. >> >> But aren't pg_stat_activity queries always cleared when you restart >> the server - because they are all disconnected... And you can't change >> track_activity_query_size without restarting. > > But not pg_stat_statistics queries, which is where I should have > probably made the note. Restarting the server won't change the length > of the field if there's already data present in pg_stat_statistics, > but upon resetting them, the field is appropriately sized. Uh, what's pg_stat_statistics? -- Magnus Hagander Me: http://www.hagander.net/ Work: http://www.redpill-linpro.com/
On 24 May 2012 13:54, Magnus Hagander <magnus@hagander.net> wrote: > On Thu, May 24, 2012 at 2:49 PM, Thom Brown <thom@linux.com> wrote: >> On 24 May 2012 13:39, Magnus Hagander <magnus@hagander.net> wrote: >>> On Thu, May 24, 2012 at 2:16 PM, Thom Brown <thom@linux.com> wrote: >>>> Hi, >>>> >>>> I attach a proposed change to the docs which points out that if the >>>> size of track_activity_query_size is changed and the is server >>>> restarted, it won't have any effect if query statistics are already >>>> present. >>> >>> But aren't pg_stat_activity queries always cleared when you restart >>> the server - because they are all disconnected... And you can't change >>> track_activity_query_size without restarting. >> >> But not pg_stat_statistics queries, which is where I should have >> probably made the note. Restarting the server won't change the length >> of the field if there's already data present in pg_stat_statistics, >> but upon resetting them, the field is appropriately sized. > > Uh, what's pg_stat_statistics? s/pg_stat_statistics/pg_stat_statements/ -- Thom
On Thu, May 24, 2012 at 2:59 PM, Thom Brown <thom@linux.com> wrote: > On 24 May 2012 13:54, Magnus Hagander <magnus@hagander.net> wrote: >> On Thu, May 24, 2012 at 2:49 PM, Thom Brown <thom@linux.com> wrote: >>> On 24 May 2012 13:39, Magnus Hagander <magnus@hagander.net> wrote: >>>> On Thu, May 24, 2012 at 2:16 PM, Thom Brown <thom@linux.com> wrote: >>>>> Hi, >>>>> >>>>> I attach a proposed change to the docs which points out that if the >>>>> size of track_activity_query_size is changed and the is server >>>>> restarted, it won't have any effect if query statistics are already >>>>> present. >>>> >>>> But aren't pg_stat_activity queries always cleared when you restart >>>> the server - because they are all disconnected... And you can't change >>>> track_activity_query_size without restarting. >>> >>> But not pg_stat_statistics queries, which is where I should have >>> probably made the note. Restarting the server won't change the length >>> of the field if there's already data present in pg_stat_statistics, >>> but upon resetting them, the field is appropriately sized. >> >> Uh, what's pg_stat_statistics? > > s/pg_stat_statistics/pg_stat_statements/ Ah, suddenly it makes sense. And in that case yes, the docs changes should go under pg_stat_statements, I believe. -- Magnus Hagander Me: http://www.hagander.net/ Work: http://www.redpill-linpro.com/
Magnus Hagander <magnus@hagander.net> writes:
> On Thu, May 24, 2012 at 2:59 PM, Thom Brown <thom@linux.com> wrote:
>>> I attach a proposed change to the docs which points out that if the
>>> size of track_activity_query_size is changed and the is server
>>> restarted, it won't have any effect if query statistics are already
>>> present.
> Ah, suddenly it makes sense.
> And in that case yes, the docs changes should go under
> pg_stat_statements, I believe.
But surely the statement is flat out wrong; or if it's not wrong,
there's a bug somewhere. We do not absorb the value of
track_activity_query_size from the stats file.
regards, tom lane
On 24 May 2012 15:19, Tom Lane <tgl@sss.pgh.pa.us> wrote: > Magnus Hagander <magnus@hagander.net> writes: >> On Thu, May 24, 2012 at 2:59 PM, Thom Brown <thom@linux.com> wrote: >>>> I attach a proposed change to the docs which points out that if the >>>> size of track_activity_query_size is changed and the is server >>>> restarted, it won't have any effect if query statistics are already >>>> present. > >> Ah, suddenly it makes sense. > >> And in that case yes, the docs changes should go under >> pg_stat_statements, I believe. > > But surely the statement is flat out wrong; or if it's not wrong, > there's a bug somewhere. We do not absorb the value of > track_activity_query_size from the stats file. Hmm... well I think I may have misinterpreted the behaviour. What I saw was the size of the query shown in pg_stat_statements remaining unchanged after restarting the server with a new track_activity_query_size value, but I'm guessing this is merely because its representation remains unchanged. If I run the same query with an extra condition on the end, it shows up as a separate row, but not truncated to the same length as the previous query. So I retract my proposed amendment as it's a falsehood. It was merely an unexpected behaviour on my part. The truth is that pre-existing queries listed in pg_stat_statements won't magically become less truncated if track_activity_query_size is increased. That only applies to new entries from that point that don't share the same query signature. -- Thom