On Mon, Feb 22, 2010 at 2:39 PM, Scott Marlowe <scott.marlowe@xxxxxxxxx> wrote: > On Mon, Feb 22, 2010 at 12:30 PM, Yang Zhang <yanghatespam@xxxxxxxxx> wrote: >> This isn't some microbenchmark. This is part of our actual analytical >> application. We're running large-scale graph partitioning algorithms. > > It's important to see how it runs if you can fit more / most of the > data set into memory by cranking up work_mem to something really big > (like a gigabyte or two) and if the query planner can switch to some > sort of hash algorithm. We're actually using a very small dataset right now. Being bounded by memory capacity is not a scalable approach for our application. > > Also, can you cluster the table on transactionid ? > We can, but that's not really addressing the core issue, which matters to us since the sort itself is only for performing a self merge join on transactionid, and the *very next step* is a group by a.tableid, a.tupleid, b.tableid, b.tupleid (i.e. requiring another sort for the group-agg). -- Yang Zhang http://www.mit.edu/~y_z/ -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
