Re: SQL:2023 JSON simplified accessor support

Hi Mark,

Thank you so much for reviewing! I have attached the new patches.

On Tue, Mar 4, 2025 at 8:05 AM Mark Dilger <mark(dot)dilger(at)enterprisedb(dot)com>
wrote:

>
> On Mon, Mar 3, 2025 at 12:23 PM Alexandra Wang <
> alexandra(dot)wang(dot)oss(at)gmail(dot)com> wrote:
>
>> I've attached v10, which addresses your feedback.
>>
>>
> Hi Alex! Thanks for the patches.
>
> In src/test/regress/sql/jsonb.sql, the section marked with "-- slices are
> not supported" should be relabeled. That comment predates these patches,
> and is now misleading.
>
> A bit further down in expected/jsonb.out, there is an expected failure,
> but no SQL comment to indicate that it is expected:
>
> +SELECT (t.jb).* FROM test_jsonb_dot_notation;
> +ERROR: missing FROM-clause entry for table "t"
> +LINE 1: SELECT (t.jb).* FROM test_jsonb_dot_notation;
>
> Perhaps a "-- fails" comment would clarify? Then, further down,
>

Fixed.

>
>
+SELECT (jb).a.**.x FROM test_jsonb_dot_notation; -- not supported
> +ERROR: syntax error at or near "**"
> +LINE 1: SELECT (jb).a.**.x FROM test_jsonb_dot_notation;
>
> I wonder if it would be better to have the parser handle this case and
> raise a ERRCODE_FEATURE_NOT_SUPPORTED instead?
>

In 0008 I added a new token named "DOUBLE_ASTERISK" to the lexers to
represent "**". Hope this helps!

> I got curious about the support for this new dot notation in the plpgsql
> parser and tried:
>
> +DO $$
> +DECLARE
> + a jsonb := '[1,2,3,4,5,6,7]'::jsonb;
> +BEGIN
> + WHILE a IS NOT NULL
> + LOOP
> + RAISE NOTICE '%', a;
> + a := a[2:];
> + END LOOP;
> +END
> +$$ LANGUAGE plpgsql;
> +NOTICE: [1, 2, 3, 4, 5, 6, 7]
> +NOTICE: [3, 4, 5, 6, 7]
> +NOTICE: [5, 6, 7]
> +NOTICE: 7
>
> which looks good! But then I tried:
>
> +DO $$
> +DECLARE
> + a jsonb := '{"": 6, "NU": [{"": [[3]]}, [6], [2], "bCi"], "aaf": [-6,
> -8]}'::jsonb;
> +BEGIN
> + WHILE a IS NOT NULL
> + LOOP
> + RAISE NOTICE '%', a;
> + a := COALESCE(a."NU", a[2]);
> + END LOOP;
> +END
> +$$ LANGUAGE plpgsql;
> +NOTICE: {"": 6, "NU": [{"": [[3]]}, [6], [2], "bCi"], "aaf": [-6, -8]}
> +ERROR: missing FROM-clause entry for table "a"
> +LINE 1: a := COALESCE(a."NU", a[2])
> + ^
> +QUERY: a := COALESCE(a."NU", a[2])
> +CONTEXT: PL/pgSQL function inline_code_block line 8 at assignment
>
> which suggests the plpgsql parser does not recognize a."NU" as we'd
> expect. Any thoughts on this?
>

Thanks for the tests! I added them to the "jsonb" regress test.

> I notice there are no changes in src/interfaces/ecpg/test, which concerns
> me. The sqljson.pgc and sqljson_jsontable.pgc files are already testing
> json handling in ecpg; perhaps just extend those a bit?
>
Thanks for bringing this up! I have added new tests in
src/interfaces/ecpg/test/sql/sqljson.pgc.

Best,
Alex