Re: Joel's Performance Issues WAS : Opteron vs Xeon

Jim, Kevin,

> > Hrm... I was about to suggest that for timing just the query (and not
> > output/data transfer time) using explain analyze, but then I remembered
> > that explain analyze can incur some non-trivial overhead with the timing
> > calls. Is there a way to run the query but have psql ignore the output?
> > If so, you could use \timing.
>
> Would timing "SELECT COUNT(*) FROM (query)" work?

Just \timing would work fine; PostgreSQL doesn't return anything until it has
the whole result set. That's why MSSQL vs. PostgreSQL timing comparisons are
deceptive unless you're careful: MSSQL returns the results on block at a
time, and reports execution time as the time required to return the *first*
block, as opposed to Postgres which reports the time required to return the
whole dataset.

--
Josh Berkus
Aglio Database Solutions
San Francisco