Re: explain plans with information about (modified) gucs

Hi,

On 2019-01-15 02:39:49 +0100, Tomas Vondra wrote:
>
>
> On 1/14/19 11:13 PM, Alvaro Herrera wrote:
> > On 2019-Jan-14, Tomas Vondra wrote:
> >
> >> The one slightly annoying issue is that currently all the options are
> >> formatted as text, including e.g. cpu_tuple_cost. That's because the GUC
> >> options may have show hook, so I can't access the value directly (not
> >> sure if there's an option around it).
> >
> > I think the problem is that you'd have to know how to print the value,
> > which can be in one of several different C types. You'd have to grow
> > some more infrastructure in the GUC tables, I think, and that doesn't
> > seem worth the trouble. Printing as text seems enough.
> >
>
> I don't think the number of formats is such a big issue - the range of
> formats is quite limited: PGC_BOOL, PGC_INT, PGC_REAL, PGC_STRING and
> PGC_ENUM. But the show hook simply returns string, and I'm not sure it's
> guaranteed it matches the raw value (afaik the assign/show hooks can do
> all kinds of funny stuff).

Yea, but the underlying values are quite useless for
humans. E.g. counting shared_buffers, wal_buffers etc in weird units is
not helpful. So you'd need to support the different units for each.

Greetings,

Andres Freund