Hi tom
At frist I have thought that the database parsed my explain statement,
so the pre-compiled execution plan will be re-used , which made the statement's second run quick.
I think that what you said is right.
Thank you
2012/11/7 Tom Lane <tgl@xxxxxxxxxxxxx>
=?UTF-8?B?6auY5YGl?= <luckyjackgao@xxxxxxxxx> writes:I think this question is based on a false premise. Why do you feel that
> It might not be a big problem in a small system.
> But when in a production environment, When I want to use explain and
> then , soon use explain analyze for the same statement,
> How can I avoid the influence of cache and get the right answer for
> evaluating purpose?
the behavior with cold caches is "the right answer", and not the behavior
with warm caches? A short-duration query like this one is not going to
be interesting at all for performance unless it's executed quite a lot,
and if it's executed quite a lot then the warm-cache result ought to be
the more representative one.
In general, trying to tune for cold-cache cases seems backwards to me.
It's much more productive to try to ensure that the caches are warm.
regards, tom lane
