Horton

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

Corey Huinker <corey.huinker@gmail.com>

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From: Corey Huinker <corey.huinker@gmail.com>
To: jian he <jian.universality@gmail.com>
Cc: Vik Fearing <vik@postgresfriends.org>, Isaac Morland <isaac.morland@gmail.com>, pgsql-hackers@lists.postgresql.org
Date: 2025-08-05T04:10:33Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Make cast functions to type money error safe

  2. Make cast function from circle to polygon error safe

  3. Make geometry cast functions error safe

  4. Make cast functions from jsonb error safe

  5. Make many cast functions error safe

  6. Add SQL/JSON query functions

  7. Add soft error handling to some expression nodes

>
>
> 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).