Re: BUG #15289: Type inference of parameters in prepared statements can sometimes fail or succeed, depending...

=?utf-8?q?PG_Bug_reporting_form?= <noreply(at)postgresql(dot)org> writes:
> Type inference of parameters in prepared statements can sometimes fail even
> though all the information is present and can be obtained if the statement
> is altered in a way that really shouldn't make any functional difference.

This is not a bug. If you don't specify a type for a parameter, the
parser attempts to infer it on first use. If the first use is
"v = $1", it will guess that $1 is meant to be the same type as v
(whose type is already known from having processed the FROM clause).
If the first use is "$1 IS NULL", there's no basis to infer a type.

One could imagine some complicated parse-time processing that tries
to defer resolving the parameter's type in hopes that some other use
will be seen later; but there is no such thing in PG, and I doubt
it will appear soon.

regards, tom lane