Re: BUG #19737: Empty `JSON_OBJECT` cannot use documented `ON NULL` or unique-key clauses

On Wed, Oct 14, 2026 at 7:06 PM Narayanan Venkateswaran
<narayananvpostgres(at)gmail(dot)com> wrote:
>
>
> Currently, calling JSON_OBJECT() without key-value arguments fails
> with a syntax error
> if modifier clauses like ABSENT ON NULL or WITH UNIQUE KEYS are specified. This
> happens because the grammar rule in gram.y handling modifier clauses
> unconditionally
> required key-value pairs.
>
> The attached patch adds conflict-free productions in gram.y to allow empty
> JSON_OBJECT() calls with NULL, UNIQUE, and RETURNING clauses.
> Regression tests have also been added to sqljson.sql covering all clause
> combinations for empty objects.
>

Thanks for the patch. It seems to work fine. I think it would be good
to make the same change for JSON_ARRAY.

One question: The commit message has this line

> The SQL standard permits calling JSON_OBJECT() with no key-value pairs
> to construct an empty JSON object while still specifying modifier
> clauses such as NULL-handling (NULL ON NULL / ABSENT ON NULL), key
> uniqueness constraints (WITH / WITHOUT UNIQUE KEYS), and the output type
> (RETURNING ...).

Is there any reference for this? I searched for this using an LLM and
found that the standard doesn't specify it but Oracle etc implement it
this way.

Thanks & Regards
Nitin Motiani,
Google