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.klaver@aklaver.com