Postgresql equivalent of Python's timeit?

[avi.e.gross at gmail.com]

Timing things that are fairly simple is hard enough to do repeatedly, but when it involves access to slower media and especially to network connections to servers, the number of things that can change are enormous. There are all kinds of caching at various levels depending on your hardware and resource contention with other programs running here and there as well as on various network-like structures and busses or just hard disks. Asking for anything to be repeated multiple times in a row as a general rule can make your results seem slower or faster depending on too many factors including what else is running on your machine.

I am wondering if an approach to running something N times that may average things out a bit is to simply put in a pause. Have your program wait a few minutes between attempts and perhaps even do other things within your loop that make it likely some of the resources you want not to be in a queue have a chance to be flushed as other things take their place. Obviously, a machine or system with lots of resources may take more effort to use enough new data that replaces the old.

Good luck. Getting reliable numbers is no easy feat as someone else may have trouble duplicating the results with a somewhat different setup.

-----Original Message-----
From: Python-list <python-list-bounces+avi.e.gross=gmail.com at python.org> On Behalf Of Albert-Jan Roskam via Python-list
Sent: Sunday, September 17, 2023 5:02 AM
To: Peter J. Holzer <hjp-python at hjp.at>
Cc: python-list at python.org
Subject: Re: Postgresql equivalent of Python's timeit?

   On Sep 15, 2023 19:45, "Peter J. Holzer via Python-list"
   <python-list at python.org> wrote:

     On 2023-09-15 17:42:06 +0200, Albert-Jan Roskam via Python-list wrote:
     >    This is more related to Postgresql than to Python, I hope this is
     ok.
     >    I want to measure Postgres queries N times, much like Python timeit
     >    (https://docs.python.org/3/library/timeit.html). I know about
     EXPLAIN
     >    ANALYZE and psql \timing, but there's quite a bit of variation in
     the
     >    times. Is there a timeit-like function in Postgresql?

     Why not simply call it n times from Python?

     (But be aware that calling the same query n times in a row is likely to
     be
     unrealistically fast because most of the data will already be in
     memory.)

   =====
   Thanks, I'll give this a shot. Hopefully the caching is not an issue if I
   don't re-use the same database connection.
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