Can you run those two queries with psql? I remember having some trouble running multiple queries in the same pgadmin process. Both would get stuck until both finished I think. I went to running a pgadmin process per query.
On Tue, Jul 28, 2009 at 9:17 AM, Robert James <srobertja...@gmail.com>wrote: > Thanks for the replies. I'm running Postgres 8.2 on Windows XP, Intel Core > Duo (though Postgres seems to use only one 1 core). > The queries are self joins on very large tables, with lots of nested loops. > > On Mon, Jul 27, 2009 at 9:40 PM, Tom Lane <t...@sss.pgh.pa.us> wrote: > >> Chris <dmag...@gmail.com> writes: >> > Robert James wrote: >> >> Hi. I'm seeing some weird behavior in Postgres. I'm running read only >> >> queries (SELECT that is - no UPDATE or DELETE or INSERT is happening at >> >> all). I can run one rather complicated query and the results come >> >> back... eventually. Likewise with another. But, when I run both >> >> queries at the same time, Postgres seems to ground to a halt. >> >> > They're probably not blocking each other but more likely you're >> > exhausting your servers resources. If they return "eventually" >> > individually, then running both at the same time will take at least >> > "eventually x2". >> >> It could be a lot more than x2. If the two queries together eat enough >> RAM to drive the machine into swapping, where it didn't swap while >> doing one at a time, the slowdown could be orders of magnitude. >> >> Watching vmstat output might be informative --- it would at least give >> an idea if the bottleneck is CPU, I/O, or swap. >> >> regards, tom lane >> > >
