Re: Getting error 42P02, despite query parameter being sent

Achilleas Mantzios <a(dot)mantzios(at)cloud(dot)gatewaynet(dot)com> writes:
> Στις 16/11/24 12:55, ο/η Max Ulidtko έγραψε:
>> The issue I'm hitting with it is exemplified by server logs like this:
>>
>> 2024-11-16 10:28:19.928 UTC [46] LOG: execute <unnamed>: CREATE VIEW
>> public.foobar (alg, hash) AS VALUES ('md5', $1);
>> 2024-11-16 10:28:19.928 UTC [46] DETAIL: parameters: $1 =
>> 'test-param-value'
>> 2024-11-16 10:28:19.928 UTC [46] ERROR: there is no parameter $1 at
>> character 57

> At least for SQL level prepared statements the statement has to be one of :
> |SELECT|, |INSERT|, |UPDATE|, |DELETE|, |MERGE|, or |VALUES|
> |so CREATE is not valid, and I guess the extended protocol prepared
> statements aint no different in this regard.

Indeed. To some extent this is an implementation limitation: the
parameter is received (and printed if you have logging enabled),
but it's not passed down to utility statements such as CREATE VIEW.
But the reason nobody's been in a hurry to lift that restriction
is that doing so would open a large can of semantic worms. In a
case like CREATE VIEW, exactly what is this statement supposed to
mean? I assume you were hoping that it would result in replacement
of the Param by a Const representing the CREATE-time value of the
parameter, but why is that a sane definition? It's certainly not
what a Param normally does. On the other hand, if CREATE VIEW
stores the Param as a Param (which is what I think would happen
if we just extended the parameter-passing plumbing), that's unlikely
to lead to a good outcome either. There might not be any $1 available
when the view is used, and if there is one it's not necessarily of
the right data type.

So, pending some defensible design for what should happen and a patch
implementing that, we've just left it at the status quo, which is that
Params are only available to the DML statements Achilleas mentioned.

regards, tom lane