Re: jsonb_array_elements issue

Mephysto <mephystoonhell(at)gmail(dot)com> writes:
> In my previous email I forgot to say that I create a cast in my database as
> I made with JSON. The cast is this:

> CREATE CAST (text AS JSONB) WITHOUT FUNCTION AS IMPLICIT;

Well, that's rather a critical bit of information :-(

> If you create this cast and you launch my select without the explicit cast,
> you should get the error. With this cast created I reported some other
> issues, so at this point my question is: can I use this implicit cast or is
> better to explicit it anytime is needed?

This cast definition is completely broken; it's astonishing that you
haven't had outright crashes, because text and jsonb do NOT have the
same underlying representation, which is what would be required to
make a cast WITHOUT FUNCTION work correctly. But this certainly
explains 'unknown type of jsonb container' errors.

You could fix that by providing a suitable casting function. I'm still
dubious that making it an implicit cast is a good idea though. The
trouble with implicit casts is that they tend to kick in when you were
not expecting them to. Past experience has suggested a rule of thumb
that implicit cross-type-category casts are best avoided, and I'd
certainly call this a type category crossing.

regards, tom lane