On Mon, Aug 8, 2016 at 7:03 PM, Bruce Momjian <bruce@momjian.us> wrote:
> It seems asking users to run pg_test_timing before deploying to check
> the overhead would be sufficient.
I'am not sure. Time measurement for waits is slightly more complicated
than a time measurement for explain analyze: a good workload plus
using gettimeofday in a straightforward manner can cause huge
overhead. Thats why a proper testing is important - if we can see a
significant performance drop if we have for example large
shared_buffers with the same concurrency, that shows gettimeofday is
too expensive to use. Am I correct, that we do not have such accurate
tests now?
My another concern is, that it is a bad idea to release a feature,
which allegedly has huge performance impact even if it is not turned
on by default. I often meet people who do not use exceptions in
plpgsql because a tip "A block containing an EXCEPTION clause is
significantly more expensive to enter ..." in PostgreSQL documentation
--
Ilya Kosmodemiansky,
PostgreSQL-Consulting.com
tel. +14084142500
cell. +4915144336040
ik@postgresql-consulting.com
