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

On Fri, Mar 13, 2026 at 11:59 AM Corey Huinker <corey(dot)huinker(at)gmail(dot)com> wrote:
>
> Can you explain this bit below?
>
> @@ -595,13 +605,23 @@ RangeVarGetRelidExtended(const RangeVar *relation, LOCKMODE lockmode,
> {
> int elevel = (flags & RVR_SKIP_LOCKED) ? DEBUG1 : ERROR;
>
> - if (relation->schemaname)
> - ereport(elevel,
> + if (relation->schemaname && elevel == DEBUG1)
> + ereport(DEBUG1,
> (errcode(ERRCODE_LOCK_NOT_AVAILABLE),
> errmsg("could not obtain lock on relation \"%s.%s\"",
> relation->schemaname, relation->relname)));
> - else
> - ereport(elevel,
> + else if (relation->schemaname && elevel == ERROR)
> + ereturn(escontext, InvalidOid,
> + errcode(ERRCODE_LOCK_NOT_AVAILABLE),
> + errmsg("could not obtain lock on relation \"%s.%s\"",
> + relation->schemaname, relation->relname));
> + else if (elevel == DEBUG1)
> + ereport(DEBUG1,
> + errcode(ERRCODE_LOCK_NOT_AVAILABLE),
> + errmsg("could not obtain lock on relation \"%s\"",
> + relation->relname));
> + else if (elevel == ERROR)
> + ereturn(escontext, InvalidOid,
>

This is for supporting casting text to regclass error safe, for example:
SELECT CAST('abc'::text as regclass default NULL on conversion error);

To do that, we need to refactor the RangeVarGetRelidExtended function
to make it error-safe.
We can also change it as:

if (relation->schemaname)
{
if (elevel == DEBUG1)
ereport(DEBUG1,
(errcode(ERRCODE_LOCK_NOT_AVAILABLE),
errmsg("could not obtain lock on relation \"%s.%s\"",
relation->schemaname, relation->relname)));
else
ereturn(escontext, InvalidOid,
errcode(ERRCODE_LOCK_NOT_AVAILABLE),
errmsg("could not obtain lock on relation \"%s.%s\"",
relation->schemaname, relation->relname));
}
else
{
if (elevel == DEBUG1)
ereport(DEBUG1,
errcode(ERRCODE_LOCK_NOT_AVAILABLE),
errmsg("could not obtain lock on relation \"%s\"",
relation->relname));
else
ereturn(escontext, InvalidOid,
(errcode(ERRCODE_LOCK_NOT_AVAILABLE),
errmsg("could not obtain lock on relation \"%s\"",
relation->relname)));
}