Re: remaining sql/json patches

On Mon, Oct 16, 2023 at 10:44 PM Anton A. Melnikov
<a.melnikov@postgrespro.ru> wrote:
> On 16.10.2023 15:49, jian he wrote:
> > add the following code after ExecEvalJsonExprCoercion if
> > (!InputFunctionCallSafe(...) works, but seems like a hack.
> >
> > if (!val_string)
> > {
> > *op->resnull = true;
> > *op->resvalue = (Datum) 0;
> > }
>
> It seems the constraint should work here:
>
> After
>
> CREATE TABLE test (
>         js text,
>         i int,
>         x jsonb DEFAULT JSON_QUERY(jsonb '[1,2]', '$[*]' WITH WRAPPER)
>         CONSTRAINT test_constraint
>                 CHECK (JSON_QUERY(js::jsonb, '$.a' RETURNING char(5) OMIT QUOTES EMPTY ARRAY ON EMPTY) > 'a')
> );
>
> INSERT INTO test_jsonb_constraints VALUES ('[]');
>
> one expected to see an error like that:
>
> ERROR:  new row for relation "test" violates check constraint "test_constraint"
> DETAIL:  Failing row contains ([], null, [1, 2]).
>
> not "INSERT 0 1"

Yes, the correct thing here is for the constraint to fail.

One thing jian he missed during the debugging is that
ExecEvalJsonExprCoersion() receives the EMPTY ARRAY value via
*op->resvalue/resnull, set by ExecEvalJsonExprBehavior(), because
that's the ON EMPTY behavior specified in the constraint.  The bug was
that the code in ExecEvalJsonExprCoercion() failed to set val_string
to that value ("[]") before passing to InputFunctionCallSafe(), so the
latter would assume the input is NULL.

--
Thanks, Amit Langote
EDB: http://www.enterprisedb.com