Re: Extract numeric filed in JSONB more effectively

>
>
> Interestingly, when I relabel both places, like this:
>
> Oid targetOid = fexpr->funcresulttype;
> Const *target = makeConst(
> OIDOID, -1, InvalidOid, sizeof(Oid),
> ObjectIdGetDatum(targetOid), false, true);
> RelabelType *rTarget = makeRelabelType((Expr *)target,
> INTERNALOID, -1, InvalidOid, COERCE_IMPLICIT_CAST);
> fexpr->funcid = new_func_id;
> fexpr->args = opexpr->args;
> fexpr->args = list_insert_nth(fexpr->args, 0, rTarget);
> expr = (Expr *)makeRelabelType((Expr *)fexpr,
> targetOid, -1, InvalidOid, COERCE_IMPLICIT_CAST);
> }
> PG_RETURN_POINTER(expr);
>
> EXPLAIN looks like this:
>
> Seq Scan on pg_temp.test_jsonb
> Output: jsonb_array_element_type(('23'::oid)::internal, test_json,
> 0), (test_json -> 0)
> Filter: (test_jsonb.json_type = 'scalarint'::text)
>
> With COERCE_IMPLICIT_CAST both places, the relabeling of the
> function result is invisible, but the relabeling of the argument
> is visible.
>
>
I think this is because get_rule_expr's showimplicit is always
true for args in this case, checking the implementation of
get_rule_expr, I found PG behavior like this in many places.

--
Best Regards
Andy Fan