On Thu, Dec 5, 2013 at 09:22:14AM -0500, Tom Lane wrote: > salah jubeh <s_jubeh@xxxxxxxxx> writes: > > When I excute a query,� the exection time is about 1 minute; however, when I execute the query with explain analyze the excution time jumps to 10 minutes. > > This isn't exactly unheard of, although it sounds like you have a > particularly bad case. Cheap commodity PCs tend to have clock hardware > that takes multiple microseconds to read ... which was fine thirty years > ago when that hardware design was set, but with modern CPUs that's > painfully slow. > > Short of getting a better machine, you might look into whether you can run > a 64-bit instead of 32-bit operating system. In some cases that allows > a clock reading to happen without a context switch to the kernel. > > > This is a little bit starnge for me; did any one experience somthing like this? Can I trust the generated plans? > > The numbers are fine as far as they go, but you should realize that the > relative cost of the cheaper plan nodes is being overstated, since the > added instrumentation cost is the same per node call regardless of how > much work happens within the node. The original poster might also want to run pg_test_timing to get hardware timing overhead: http://www.postgresql.org/docs/9.3/static/pgtesttiming.html -- Bruce Momjian <bruce@xxxxxxxxxx> http://momjian.us EnterpriseDB http://enterprisedb.com + Everyone has their own god. + -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
