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From: jian he <jian.universality@gmail.com>
Date: Wed, 27 Aug 2025 12:15:06 +0800
Message-ID: 
 <CACJufxFg0Li_skG2NCFg=EneaqhnPBrVDLeAm6yVFWkdoY3y5w@mail.gmail.com>
Subject: Re: SQL:2023 JSON simplified accessor support
To: Alexandra Wang <alexandra.wang.oss@gmail.com>
Cc: Nikita Malakhov <hukutoc@gmail.com>,
 Vik Fearing <vik@postgresfriends.org>,
	Mark Dilger <mark.dilger@enterprisedb.com>,
 Matheus Alcantara <matheusssilv97@gmail.com>,
	Peter Eisentraut <peter@eisentraut.org>,
 Andrew Dunstan <andrew@dunslane.net>,
	Nikita Glukhov <glukhov.n.a@gmail.com>,
 PostgreSQL Hackers <pgsql-hackers@postgresql.org>,
	"David E. Wheeler" <david@justatheory.com>
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On Tue, Aug 26, 2025 at 11:53=E2=80=AFAM Alexandra Wang
<alexandra.wang.oss@gmail.com> wrote:
>
> Hi Jian,
>
> I=E2=80=99ve attached v14, which includes only indentation and comment ch=
anges
> from v13.
>

hi.
still reviewing v14-0001 to v14-0005.

I am confused by the comments in jsonb_subscript_transform
""
     * (b) jsonb_subscript_make_jsonpath() examined the first indirection
     * element but could not turn it into a JsonPath component (for example=
,
     * ['a']).
"""
CREATE TABLE ts2 AS SELECT '{"a": "b"}' ::jsonb jb;
SELECT (jb)['a'] FROM ts2;
SELECT (jb).a['a'] FROM ts2;
in these two cases, ['a'], it won't reach jsonb_subscript_make_jsonpath,
because jsonb_check_jsonpath_needed will return false.

maybe I am missing something,
for the above point b, can you use some SQL example to explain it?


make_jsonpath_item_expr(ParseState *pstate, Node *expr, List **exprs)
if expr satisfies the condition, then append the transformed expr to List e=
xprs
if not returns NULL.
The list append logic is within make_jsonpath_item_int.
seems not that intuitive (another level of indirection)
maybe we don't need make_jsonpath_item_int.

Another reason would be in make_jsonpath_item_int it's not easy found
out that exprs actually refers to SubscriptingRef->refupperindexpr

also v14-0006-Implement-Jsonb-subscripting-with-slicing.patch also doesn't =
use
make_jsonpath_item_int that much frequently.
--------------------------------
in v14-0005-Implement-read-only-dot-notation-for-jsonb.patch

+ * In addition to building the JsonPath expression, this function populate=
s
+ * the following fields of the given SubscriptingRef:
+ * - refjsonbpath: the generated JsonPath
+ * - refupperindexpr: upper index expressions (object keys or array indexe=
s)
+ * - reflowerindexpr: lower index expressions, remains NIL as slices
are not yet supported.

"reflowerindexpr" changed in v14-0006, so "reflowerindexpr" comments
in v14-0006 need to change.
but "reflowerindexpr" we didn't touch in v14-0005, so the
"reflowerindexpr" comments look weird.


+SELECT (jb).a['b'] FROM test_jsonb_dot_notation; -- returns NULL due
to strict mode
we can not specify strict just like,  ``select 'strict $'::jsonpath;``
all the patches in here are default to lax mode.
so I am confused by this comment. ("strict mode").