Re: Measuring CPU time use? (Another stupid question)

Joe Conway <mail@joeconway.com> writes:
> Jessica Blank wrote:
>> So I guess what I'm saying is that I don't care so much about CPU time, or
>> I/O time, but *TOTAL* time. How long it takes from the instant the query
>> hits Postgres to the instant I get my results back...

> That's pretty much exactly what EXPLAIN ANALYZE does for you. And along with
> it, you get other useful information to help you improve the query.

Also, in 7.3 psql has a "\timing" setting that automatically gives you
elapsed time for each query.

I concur with the recommendation to pay more attention to elapsed time
than CPU time (even if you could get the latter, which you can't
easily).

If you really feel a need for CPU time, you could turn on
"log_statement_stats" (that's what current sources call it anyway,
but I think Bruce renamed it from something else recently) and then
look in the postmaster log for entries like so:

LOG:  QUERY STATISTICS
! system usage stats:
!       3.843989 elapsed 2.220000 user 0.340000 system sec
!       [2.260000 user 0.360000 sys total]
!       1797/0 [1874/4] filesystem blocks in/out
!       0/0 [0/1] page faults/reclaims, 0 [0] swaps
!       0 [0] signals rcvd, 0/144 [5/149] messages rcvd/sent
!       1410/238 [1458/246] voluntary/involuntary context switches
! buffer usage stats:
!       Shared blocks:       1799 read,          0 written, buffer hit rate = 7.08%
!       Local  blocks:          0 read,          0 written, buffer hit rate = 0.00%
!       Direct blocks:          0 read,          0 written

But I think EXPLAIN ANALYZE is much more useful.

            regards, tom lane