On 2017-09-27 15:30:45 -0400, Robert Haas wrote: > On Wed, Sep 27, 2017 at 1:40 PM, Andres Freund <and...@anarazel.de> wrote: > > I don't think you can even measure the overhead of building the > > table. This is inserting ~8k rows in an accurately sized hashtable - a > > vanishingly small amount of time in comparison to the backend startup > > time (and even more so postmaster startup). My measurement shows it > > takes about 0.4 ms to build (gdb in, query, reset oid2builtins = 0, > > query - repeat a couple times). > > 0.4ms isn't negligible as a fraction of backend startup time, is it?
Well, on linux you'd only have this on postmaster startup. > I think backend startup time is a few milliseconds. > > $ echo '\set x 1' > x.txt > $ pgbench -n -C -c 1 -f x.txt -T 10 > transaction type: x.txt > scaling factor: 1 > query mode: simple > number of clients: 1 > number of threads: 1 > duration: 10 s > number of transactions actually processed: 5091 > latency average = 1.965 ms > tps = 508.866931 (including connections establishing) > tps = 12909.303693 (excluding connections establishing) I had tried this with an actual simplistic query, and the difference was either nonexistant, or below in the noise. I didn't do a pgbench run that doesn't actually do anything in the backend - doesn't seem like a meaningful thing to measure? Greetings, Andres Freund -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers