On 2013-09-10 08:45:33 -0400, Andrew Dunstan wrote: > > On 09/10/2013 08:20 AM, Andres Freund wrote: > > >A backtrace for this would be useful. Alternatively you could recompile > >postgres using -fno-omit-frame-pointer in CFLAGS and use perf record -g. > > It's using a custom build, so this should be doable. Great. > >Any chance you have older prepared xacts, older sessions or something > >like that around? I'd expect heap_prune* to be present in workloads that > >spend significant time in heap_hot_search_buffer... > > > Not sure about prepared transactions. There are certainly probably old > prepared statements around, and long running transactions alongside this > one. Ok, long running transactions will do the trick. I quicky checked and doing an index lookup for min/max histogram lookups was added *after* 8.4 which would explain why you're not seing the issue there (c.f. 40608e7f949fb7e4025c0ddd5be01939adc79eec). It getting slower and slower during a testrun would be explained by the additional tuple versions amassing which cannot be marked dead because of older transactions around. I guess those are also part of the test? If I interpret things correctly you're using serializable? I guess there is no chance to use repeatable read instead? Greetings, Andres Freund -- Andres Freund http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
