Re: plpgsql: ambiguous column reference in ON CONFLICT clause

On 2/6/23 09:46, Torsten Förtsch wrote:
> Is there a way to prevent this from happening? I know I can use the PK
> constraint name or rename the OUT variable i. The question is can this
> be resolved while keeping the arbiter inference and the variable name.
>
> CREATE TABLE x.x (
>     i INT PRIMARY KEY
> );
>
> CREATE OR REPLACE FUNCTION x.ins(p_i INT, OUT i INT)
> LANGUAGE plpgsql AS $$
>   BEGIN
>     INSERT INTO x.x(i)
>     SELECT p_i
>         ON CONFLICT (i) DO NOTHING;
>   END
> $$;
>
> postgres=# select * from x.ins(1);
> ERROR:  column reference "i" is ambiguous
> LINE 3:         ON CONFLICT (i) DO NOTHING
>                             ^
> DETAIL:  It could refer to either a PL/pgSQL variable or a table column.
> QUERY:  INSERT INTO x.x(i)
>     SELECT p_i
>         ON CONFLICT (i) DO NOTHING
> CONTEXT:  PL/pgSQL function x.ins(integer) line 3 at SQL statement
>
> The conflicting variable is the OUT parameter of the function.
>
> Normally, I'd suggest to fully qualify the name but the following or
> similar is a syntax error:
>
>     INSERT INTO x.x(i) AS t
>     SELECT p_i
>         ON CONFLICT (t.i) DO NOTHING;
>
> According to the documentation in
> https://www.postgresql.org/docs/current/plpgsql-implementation.html
> <https://www.postgresql.org/docs/current/plpgsql-implementation.html>:
>
> > Query parameters will only be substituted in places where they are
> syntactically permissible.

See:

https://www.postgresql.org/docs/current/plpgsql-implementation.html#PLPGSQL-VAR-SUBST

for your choices.

>
> and
>
> > Another way to understand this is that variable substitution can only
> insert data values into an SQL command; it cannot dynamically change
> which database objects are referenced by the command.
>
> After reading this I am wondering if the current behavior is actually a bug.
>
> Thanks,
> Torsten

--
Adrian Klaver
adrian(dot)klaver(at)aklaver(dot)com