Date: Thu, 17 Dec 2020 21:00:33 +0100
From: Dmitry Dolgov <9erthalion6@gmail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Pavel Stehule <pavel.stehule@gmail.com>,
	Andres Freund <andres@anarazel.de>,
	Alexander Korotkov <aekorotkov@gmail.com>,
	Justin Pryzby <pryzby@telsasoft.com>,
	David Steele <david@pgmasters.net>,
	Nikita Glukhov <n.gluhov@postgrespro.ru>,
	Alvaro Herrera <alvherre@2ndquadrant.com>,
	David Fetter <david@fetter.org>,
	Thomas Munro <thomas.munro@gmail.com>,
	Oleksandr Shulgin <oleksandr.shulgin@zalando.de>,
	Robert Haas <robertmhaas@gmail.com>,
	Michael Paquier <michael.paquier@gmail.com>,
	Oleg Bartunov <obartunov@gmail.com>,
	Peter Eisentraut <peter.eisentraut@2ndquadrant.com>,
	PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Subject: Re: [HACKERS] [PATCH] Generic type subscripting
Message-ID: <20201217200033.qdyjv4iimwyglnwt@localhost>
References: <3544235.1607482944@sss.pgh.pa.us>
 <3635350.1607536188@sss.pgh.pa.us>
 <20201209183704.x5ue5rctdwmhmlmy@localhost>
 <3674425.1607540422@sss.pgh.pa.us>
 <3724341.1607551174@sss.pgh.pa.us>
 <CAFj8pRCbH_48FfTGHczts8hTA4e0eKhcs5UwdybotoQEH_Pfcg@mail.gmail.com>
 <20201211151957.wqlnxdqjwsd7azzd@localhost>
 <4110100.1607701087@sss.pgh.pa.us>
 <20201217182003.nrhxqqiutfwjesen@localhost>
 <107232.1608230957@sss.pgh.pa.us>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <107232.1608230957@sss.pgh.pa.us>
Precedence: bulk

> On Thu, Dec 17, 2020 at 01:49:17PM -0500, Tom Lane wrote:
> Dmitry Dolgov <9erthalion6@gmail.com> writes:
> > While rebasing the jsonb patch I found out that the current subscripting
> > assignment implementation in transformAssignmentIndirection always
> > coerce the value to be assigned to the type which subscripting result
> > suppose to have (refrestype). For arrays it's fine, since those two
> > indeed must be the same, but for jsonb (and for hstore I guess too) the
> > result of subscripting is always jsonb (well, text type) and the
> > assigned value could be of some other type. This leads to assigning
> > everything converted to text.
>
> So ... what's the problem with that?  Seems like what you should put
> in and what you should get out should be the same type.
>
> We can certainly reconsider the API for the parsing hook if there's
> really a good reason for these to be different types, but it seems
> like that would just be encouraging poor design.

To be more specific, this is the current behaviour (an example from the
tests) and it doesn't seem right:

    =# update test_jsonb_subscript
       set test_json['a'] = 3 where id = 1;

    UPDATE 1

    =# select jsonb_typeof(test_json->'a')
       from test_jsonb_subscript where id = 1;

     jsonb_typeof
     --------------
      string

    =# update test_jsonb_subscript
       set test_json = jsonb_set(test_json, '{a}', '3') where id = 1;

    UPDATE 1
    =# select jsonb_typeof(test_json->'a')
       from test_jsonb_subscript where id = 1;

     jsonb_typeof
     --------------
      number