Horton

Re: BUG #19046: Incorrect result when using json_array() with column reference in subquery combined with RIGHT JOIN

Richard Guo <guofenglinux@gmail.com>

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From: Richard Guo <guofenglinux@gmail.com>
To: Tender Wang <tndrwang@gmail.com>
Cc: runyuan@berkeley.edu, pgsql-bugs@lists.postgresql.org, Tom Lane <tgl@sss.pgh.pa.us>
Date: 2025-09-10T13:29:41Z
Lists: pgsql-bugs

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Treat JsonConstructorExpr as non-strict

  2. Avoid inserting PlaceHolderVars in cases where pre-v16 PG did not.

On Wed, Sep 10, 2025 at 9:31 PM Tender Wang <tndrwang@gmail.com> wrote:
>> PG Bug reporting form <noreply@postgresql.org> 于2025年9月10日周三 18:22写道：
>>> SELECT sub.c FROM
>>> (SELECT json_array(3, 2, t.c) AS c FROM t) AS sub
>>> RIGHT JOIN t ON FALSE;

> diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c
> index 6f0b338d2cd..5ef364b7f7c 100644
> --- a/src/backend/optimizer/util/clauses.c
> +++ b/src/backend/optimizer/util/clauses.c
> @@ -1115,6 +1115,8 @@ contain_nonstrict_functions_walker(Node *node, void *context)
>                 return true;
>         if (IsA(node, BooleanTest))
>                 return true;
> +       if (IsA(node, JsonConstructorExpr))
> +               return true;
>
> I added the above codes, then the query returned the correct result.
> I didn't dig more the details. Any thought?

Yeah, JsonConstructorExpr should not be treated as a non-strict
construct.  This fix looks correct to me.

I'm wondering if this is the only case we've overlooked.  How about
other Json-related expressions?

- Richard