Re: CAST(... ON DEFAULT) - WIP build on top of Error-Safe User Functions

>
>
> In the end, it seems we need to make all these functions in the below
> query error safe.
> select castsource::regtype, casttarget::regtype, castfunc,
> castcontext,castmethod, pp.prosrc, pp.proname from pg_cast pc join pg_proc
> pp on
> pp.oid = pc.castfunc and pc.castfunc > 0
> order by castsource::regtype;
> It's a lot of work, but seems doable, after playing around with it.
>

It is do-able. But that's just the cast functions that are part of core
postgres.

>
>
> I don't think we need to change the pg_cast catalog entry,
> we just need to make these function (pg_cast.castmethod) errors safe.

That would break any user-defined cast functions that were not also error
safe, which is to say all of them.

We need a way for user-defined cast functions to indicate whether or not
they are error safe, and handle both situations accordingly (i.e. fail a
CAST ON DEFAULT when the user-defined cast is not error-safe).