Re: pg_stat_statements fingerprinting logic and ArrayExpr

On Tue, Dec 10, 2013 at 1:09 PM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> I am very wary of implementing special-case logic here even though I
> know it could be useful to some people, simply because I fear that
> there could be a near-infinite variety of situations where, in a
> particular environment, a particular distinction isn't important.

I am too, which is why I asked.

We're already in the business of deciding what is and isn't essential
to a query in this way. For example, we already determine that
Var.varcollid shouldn't appear in a query jumble - there is no better
reason for that then "it would hurt more than it helped", even though
it's possible that someone could care about such a distinction. Now, I
have no intention of avoiding the issue with a relativistic argument
("who is to say what the essential nature of a query is anyway?"), but
I know doctrinarianism isn't helpful either.

I do think I know who should determine what is the essential nature of
a query for fingerprinting purposes: we should. We should pick the
scheme that is most widely useful, while weighing the worst case. I'm
not asserting that this is closer to that, but it might be.

--
Peter Geoghegan