On Fri, Jan 31, 2014 at 5:07 AM, Mitsumasa KONDO <kondo.mitsum...@gmail.com> wrote: > And past result shows that your patch's most weak point is that deleting > most old statement > and inserting new old statement cost is very high, as you know.
No, there is no reason to imagine that entry_dealloc() is any slower, really. There will perhaps be some additional contention with shared lockers, but that isn't likely to be a major aspect. When the hash table is full, in reality at that point it's very unlikely that there will be two simultaneous sessions that need to create a new entry. As I said, on many of the systems I work with it takes weeks to see a new entry. This will be especially true now that the *.max default is 5,000. > It accelerate to affect > update(delete and insert) cost in pg_stat_statements table. So you proposed > new setting > 10k in default max value. But it is not essential solution, because it is > also good perfomance > for old pg_stat_statements. I was merely pointing out that that would totally change the outcome of your very artificial test-case. Decreasing the number of statements to 5,000 would too. I don't think we should assign much weight to any test case where the large majority or all statistics are wrong afterwards, due to there being so much churn. -- Peter Geoghegan -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
