On 12/28/12 5:11 PM, Heikki Linnakangas wrote: > > As it happens, I just spent a lot of time today narrowing down yet > another report of a regression in 9.2, when running DBT-2: > http://archives.postgresql.org/pgsql-performance/2012-11/msg00007.php. > It looks like that is also caused by the plancache changes. DBT-2 > implements the transactions using C functions, which use SPI_execute() > to run all the queries. > > It looks like the regression is caused by extra copying of the parse > tree and plan trees. Node-copy-related functions like AllocSetAlloc and > _copy* are high in the profile, They are also high in the 9.1 profile, > but even more so in 9.2. > > I hacked together a quick&dirty patch to reduce the copying of > single-shot plans, and was able to buy back much of the regression I was > seeing on DBT-2. Patch attached. But of course, DBT-2 really should be > preparing the queries once with SPI_prepare, and reusing them thereafter.
I was recently profiling an application that uses a fair amount of PL/pgSQL with dynamic queries and also noticed AllocSetAlloc high in the profile. I was getting suspicious now and compared 9.1 and 9.2 performance: 9.2 is consistently about 3% slower. Your patch doesn't seem to have a measurable effect, but it might be if I ran the test for longer. -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers