Re: PoC plpgsql - possibility to force custom or generic plan

2017-09-11 14:44 GMT+02:00 Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>:

> Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com> writes:
> > On 9/8/17 13:14, Simon Riggs wrote:
> >> 2. Allow a SET to apply only for a single statement
> >> SET guc1 = x, guc2 = y FOR stmt
> >> e.g. SET max_parallel_workers = 4 FOR SELECT count(*) FROM bigtable
> >> Internally a GUC setting already exists for a single use, via
> >> GUC_ACTION_SAVE, so we just need to invoke it.
>
> > This doesn't read well to me. It indicates to me "make this setting for
> > this query [in case I run it later]", but it does not indicate that the
> > query will be run.
>
> Robert's original LET ... IN ... syntax proposal might be better from that
> standpoint.
>

From my perspective Robert's proposal is not targeted to PLpgSQL well,
because it doesn't allow to choose granularity.

I am not sure what is result from this discussion:

1. this feature is wanted

2. a opened question is the syntax

I am sure so GUC are not a good design solution for PL/pgSQL. Robert's
proposal does thing bit better, but it has sense more for another
environments than PLpgSQL - more, it allows more degree of freedom what has
sense for PLpgSQL.

There is possibility to introduce new compile option #option to disable
plan cache on function scope. Do you think so it is acceptable solution? It
is step forward.

Regards

Pavel

> regards, tom lane
>