Hello
It is little bit strange - can you send a info about your PostgreSQL version, send a query, and table description? In this case, PostgreSQL should to use a hash aggregate, but from some strange reason, pg didn't do it. Second strange issue is speed of external sort - it is less than I can expect. What I know - a usual advice for MS Win is setting minimal shared bufferes - 512MB can be too much there. Regards Pavel Stehule 2013/8/26 Adam Ma'ruf <adam.ma...@gmail.com> > Hi, > > I wasn't whether or not to mail to the novice mailing list of this one. > Since this is performance related I'm posting it here, but I am definitely > a novice at postgresql - converting from mssql just now. > > I have a ~2.5gb table with ~5M rows of data. A query that groups by two > fields and sums a floating field takes approximately 122 seconds. The > equivalent query takes ~ 8seconds in my previous sql server express > installation. > > I've tried to vary the parameters in postgresql.conf: > I've tried wavering shared buffers from 512mb to 4000mb > and working_mem from 64mb to 4000mb (i thought this might be the answer > since the execution plan (referenced below) indicates that the sort relies > on an External Merge Disk method) > I've increased the default_statistics_target to 10000 and full vacuum > analyzed > I realize there are no indexes on this table. My main concern is why I > can't get this to run as fast as in sql server express (which also has no > indexes, and the same query takes about 8 seconds) > > My system: Windows Professional 64-bit > 8 gb of ram > Intel i5-220M CPU @ 2.5GHz > > Here is the link to the execution plan: http://explain.depesz.com/s/Ytx3 > > Thanks a lot in advance and do let me know if you require any more > information to make an informed opinion, > A >
