st 31. 8. 2022 v 17:50 odesílatel Pavel Stehule <pavel.steh...@gmail.com> napsal:
> Hi > > > st 31. 8. 2022 v 17:34 odesílatel Drouvot, Bertrand <bdrou...@amazon.com> > napsal: > >> Hi hackers, >> >> While query jumbling is provided for function calls that’s currently not >> the case for procedures calls. >> The reason behind this is that all utility statements are currently >> discarded for jumbling. >> >> We’ve recently seen performance impacts (LWLock contention) due to the >> lack of jumbling on procedure calls with pg_stat_statements and >> pg_stat_statements.track_utility enabled (think an application with a high >> rate of procedure calls with unique parameters for each call). >> >> Jeremy has had this conversation on twitter (see >> https://twitter.com/jer_s/status/1560003560116342785) and Nikolay >> reported that he also had to work on a similar performance issue with SET >> being used. >> >> That’s why we think it would make sense to allow jumbling for those 2 >> utility statements: CALL and SET. >> >> Please find attached a patch proposal for doing so. >> >> With the attached patch we would get things like: >> CALL MINUS_TWO(3); >> CALL MINUS_TWO(7); >> CALL SUM_TWO(3, 8); >> CALL SUM_TWO(7, 5); >> set enable_seqscan=false; >> set enable_seqscan=true; >> set seq_page_cost=2.0; >> set seq_page_cost=1.0; >> >> postgres=# SELECT query, calls, rows FROM pg_stat_statements; >> query | calls | rows >> -----------------------------------+-------+------ >> set seq_page_cost=$1 | 2 | 0 >> CALL MINUS_TWO($1) | 2 | 0 >> set enable_seqscan=$1 | 2 | 0 >> CALL SUM_TWO($1, $2) | 2 | 0 >> >> Looking forward to your feedback, >> > The idea is good, but I think you should use pg_stat_functions instead. > Maybe it is supported already (I didn't test it). I am not sure so SET > statement should be traced in pg_stat_statements - it is usually pretty > fast, and without context it says nothing. It looks like just overhead. > I was wrong - there is an analogy with SELECT fx, and the statistics are in pg_stat_statements, and in pg_stat_function too. Regards Pavel > > Regards > > Pavel > > >> Thanks, >> >> Jeremy & Bertrand >> >> -- >> Bertrand Drouvot >> Amazon Web Services: https://aws.amazon.com >> >>
