Re: strange

=?UTF-8?Q?Filip_Rembia=C5=82kowski?= <plk.zuber@gmail.com> writes:
> For the record, I've recently observed such behaviour on non-cheap
> 64bit server harware.

> That was Pg 8.4.0. hardware specs available on request.

> EXPLAIN ANALYZE SELECT was over 2 times slower that SELECT. repeatedly.

> Answering an obligatory question: NO virtualization (vmware/xen/other) there.

> Question:
> Is there anything as normal, accepted level of performance degradation
> when using EXPLAIN ANALYZE compared to plain query?

You should certainly not expect it to be free, if that's what you mean.
2X penalty on a very cheap plan node (such as a seqscan with no filter)
doesn't surprise me much.

BTW, it occurs to me that gettimeofday's microsecond resolution doesn't
really get the job done anymore for such cheap plan nodes.  I wonder if
we should be trying to use clock_gettime() where available.

            regards, tom lane