Re: SQL:2023 JSON simplified accessor support

From: Alexandra Wang <alexandra(dot)wang(dot)oss(at)gmail(dot)com>
To: Jelte Fennema-Nio <postgres(at)jeltef(dot)nl>
Cc: Mark Dilger <mark(dot)dilger(at)enterprisedb(dot)com>, Matheus Alcantara <matheusssilv97(at)gmail(dot)com>, Peter Eisentraut <peter(at)eisentraut(dot)org>, Andrew Dunstan <andrew(at)dunslane(dot)net>, Nikita Glukhov <glukhov(dot)n(dot)a(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>, "David E(dot) Wheeler" <david(at)justatheory(dot)com>, jian he <jian(dot)universality(at)gmail(dot)com>
Subject: Re: SQL:2023 JSON simplified accessor support
Date: 2025-07-09 08:10:36
Message-ID: CAK98qZ05OyQE7UW6+W27fnMyTdfqXvU9Fw6D35m0bMNtNySEgQ@mail.gmail.com
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Hi Jelte,

On Sat, Jun 28, 2025 at 4:52 PM Jelte Fennema-Nio <postgres(at)jeltef(dot)nl>
wrote:

> On Thu, 13 Mar 2025 at 15:02, Alexandra Wang
> <alexandra(dot)wang(dot)oss(at)gmail(dot)com> wrote:
> > I have attached the new patches.
>
> Okay I finally found the time to look at this. I created a draft PR
> for pg_duckdb[1] to see if I would run into issues. There was only one
> real issue I found by doing this. The .* syntax is encoded as NULL in
> refupperindexpr, but that is currently already a valid representation
> of a slice operation without specifying upper or lower. The easiest
> way to reproduce the problem is:
>
> CREATE TABLE arr(a int[]);
> explain (verbose) SELECT a[:] FROM arr;
> QUERY PLAN
> ───────────────────────────────────────────────────────────────
> Seq Scan on public.arr (cost=0.00..23.60 rows=1360 width=32)
> Output: a.*
>
> That last line should instead be
> Output: a[:]
>
> So I think we need to add a new Star node type, that represents the *
> literal after parsing.
>
> I haven't looked too closely at the code yet.
>

Thank you so much for testing and reviewing, I really appreciate it! I
fixed the EXPLAIN in v12 by adding a Star node, as you suggested.
Looking forward to your thoughts when you have time for a further
review!

Best,
Alex

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