Date: Wed, 8 Apr 2020 11:31:20 +0200
From: Julien Rouhaud <rjuju123@gmail.com>
To: Fujii Masao <masao.fujii@oss.nttdata.com>
Cc: legrand legrand <legrand_legrand@hotmail.com>,
	pgsql-hackers@postgresql.org
Subject: Re: Planning counters in pg_stat_statements (using pgss_store)
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On Wed, Apr 08, 2020 at 05:37:27PM +0900, Fujii Masao wrote:
> 
> 
> On 2020/04/03 16:26, Julien Rouhaud wrote:
> > On Thu, Apr 02, 2020 at 01:04:28PM -0700, legrand legrand wrote:
> > > Fujii Masao-4 wrote
> > > > On 2020/04/01 18:19, Fujii Masao wrote:
> > > > 
> > > > Finally I pushed the patch!
> > > > Many thanks for all involved in this patch!
> > > > 
> > > > As a remaining TODO item, I'm thinking that the document would need to
> > > > be improved. For example, previously the query was not stored in pgss
> > > > when it failed. But, in v13, if pgss_planning is enabled, such a query is
> > > > stored because the planning succeeds. Without the explanation about
> > > > that behavior in the document, I'm afraid that users will get confused.
> > > > Thought?
> > > 
> > > Thank you all for this work and especially to Julian for its major
> > > contribution !
> > 
> > 
> > Thanks a lot to everyone!  This was quite a long journey.
> > 
> > 
> > > Regarding the TODO point: Yes I agree that it can be improved.
> > > My proposal:
> > > 
> > > "Note that planning and execution statistics are updated only at their
> > > respective end phase, and only for successfull operations.
> > > For exemple executions counters of a long running SELECT query,
> > > will be updated at the execution end, without showing any progress
> > > report in the interval.
> > > Other exemple, if the statement is successfully planned but fails in
> > > the execution phase, only its planning statistics are stored.
> > > This may give uncorrelated plans vs calls informations."
> 
> Thanks for the proposal!
> 
> > There are numerous reasons for lack of correlation between number of planning
> > and number of execution, so I'm afraid that this will give users the false
> > impression that only failed execution can lead to that.
> > 
> > Here's some enhancement on your proposal:
> > 
> > "Note that planning and execution statistics are updated only at their
> > respective end phase, and only for successful operations.
> > For example the execution counters of a long running query
> > will only be updated at the execution end, without showing any progress
> > report before that.
> 
> Probably since this is not the example for explaining the relationship of
> planning and execution stats, it's better to explain this separately or just
> drop it?
> 
> What about the attached patch based on your proposals?
> 

Thanks Fuji-san, it looks perfect to me!