Por favor, no quiero seguir recibiendo mensajes
Tom Lane escribió:
Richard Huxton <dev@xxxxxxxxxxxx> writes:
If you connect via psql and then (as root, in another terminal) do:
ps auxw | grep postgres
you should see the backend that corresponds to your psql connection.
strace -p <pid>
should then show system calls as they are executed (assuming you have it
installed). Execute the explain, and see what is output.
Mine flies past, but is composed almost entirely of "gettimeofday" calls
(10,000 of them) apart from at the very end where we get some write and
send/recv calls (to print the explain results). I've heard of some
people having slow "gettimeofday" calls, but not on linux. On the other
hand, that seems to be the main difference between strace output with
"not in" compared to "in".
AFAICT Sergey is complaining about the speed of EXPLAIN, *not* EXPLAIN
ANALYZE. There'd only be a lot of gettimeofday calls in an EXPLAIN
ANALYZE test.
The whole thing doesn't make a lot of sense to me either. All the
slowdown explanations I can think of would apply as much or more to the
IN case...
regards, tom lane
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