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

On Tue, Mar 19, 2019 at 2:45 PM Maksim Milyutin <milyutinma(at)gmail(dot)com> wrote:
>
> But I think that enough to integrate into core the query normalization
> routine and store generalized query strings (from which the queryId is
> produced) in shared memory (for example, hashtable that maps queryId to
> the text representation of generalized query).

That's more or less how pg_stat_statements was previously behaving,
and it had too many problems. Current implementation, with an
external file, is a better alternative.

> And activate
> normalization routine and filling the table of generalized queries by
> specified GUC.
>
> This allows to unbind extensions that require queryId from using
> pg_stat_statements and consider such computing of queryId as canonical.

The problem I see with this approach is that if you want a different
implementation, you'll have to reimplement the in-core normalised
queries saving and retrieval, but with a different set of SQL-visible
functions. I don't think that's it's acceptable, unless we add a
specific hook for query normalisation and queryid computing. But it
isn't ideal either, as it would be a total mess if someone changes the
implementation without resetting the previously saved normalised
queries.