Re: Feature improvement: can we add queryId for pg_catalog.pg_stat_activity view?

On Mon, Oct 12, 2020 at 02:26:15PM -0400, Tom Lane wrote:
> Robert Haas <robertmhaas@gmail.com> writes:
> > I don't really understand how a version number helps. It's not like
> > there is going to be a v2 that is in all ways better than v1. If there
> > are different algorithms here, they are going to be customized for
> > different needs.
> 
> Yeah, I agree --- a version number is the wrong way to think about this.
> It's gonna be more like algorithm foo versus algorithm bar versus
> algorithm baz, where each one is better for a specific set of use-cases.
> Julien already noted the point about hashing object OIDs versus object
> names; one can easily imagine disagreeing with pg_stat_statement's
> choices about ignoring values of constants; other properties of statements
> might be irrelevant for some use-cases; and so on.

The version number was to invalidate _all_ query hashes if the
algorithm is slightly modified, rather than invalidating just some of
them, which could lead to confusion.  The idea of selectable hash
algorithms is nice if people feel there is sufficient need for that.

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

  The usefulness of a cup is in its emptiness, Bruce Lee