Josh Berkus <josh@agliodbs.com> writes:
> Yeah, I believe the core problem is that Postgres currently doesn't have
> any way to have variadic return times from a function which don't match
> variadic input types. Returning a value as an actual numeric from JSONB
> would require returning a numeric from a function whose input type is
> text or json. So a known issue but one which would require a lot of
> replumbing to fix.
Well, it'd be easy to fix if we were willing to invent distinct operators
depending on which type you wanted out (perhaps ->> for text output as
today, add ->># for numeric output, etc). Doesn't seem terribly nice
from a usability standpoint though.
The usability issue could be fixed by teaching the planner to fold a
construct like (jsonb ->> 'foo')::numeric into (jsonb ->># 'foo').
But I'm not sure how we do that except in a really ugly and ad-hoc
fashion.
regards, tom lane