Re: compute_query_id and pg_stat_statements

On Thu, May 13, 2021 at 02:29:09PM -0400, Tom Lane wrote:
> Stephen Frost <sfrost@snowman.net> writes:
> > There's a ridiculously simple option here which is: drop the idea that
> > we support an extension redefining the query id and then just make it
> > on/off with the default to be 'on'.
> 
> I do not think that defaulting it to 'on' is acceptable unless you can
> show that the added overhead is negligible.  IIUC the measurements that
> have been done show the opposite.

Agreed.

> Maybe we should revert this thing pending somebody doing the work to
> make a version of queryid labeling that actually is negligibly cheap.
> It certainly seems like that could be done; one more traversal of the
> parse tree can't be that expensive in itself.  I suspect that the
> performance problem is with the particular hashing mechanism that
> was used, which looks mighty ad-hoc anyway.

I was surprised it was ~2%.

-- 
  Bruce Momjian  <bruce@momjian.us>        https://momjian.us
  EDB                                      https://enterprisedb.com

  If only the physical world exists, free will is an illusion.