From: Tom Lane <tgl@sss.pgh.pa.us>
To: Robert Haas <robertmhaas@gmail.com>
cc: Andres Freund <andres@anarazel.de>, Dmitry Dolgov <9erthalion6@gmail.com>,
        Michael Paquier <michael.paquier@gmail.com>,
        Arthur Zakirov <a.zakirov@postgrespro.ru>,
        Oleg Bartunov <obartunov@gmail.com>,
        Peter Eisentraut <peter.eisentraut@2ndquadrant.com>,
        David Steele <david@pgmasters.net>,
        PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: [HACKERS] [PATCH] Generic type subscripting
In-reply-to: 
 <CA+Tgmobvw+V3yG4LH3VzmR=9ais8fWFgeym1kYpZbjGLDzA3ig@mail.gmail.com>
References: 
 <CA+q6zcUws7270pFKgT7G0jFuLxmCaBLqPL0o4sfgfLnRBGg9gg@mail.gmail.com>
 <20171116114016.GA21162@zakirov.localdomain>
 <CA+q6zcUn+9OnuMh3Mvu=XaNpSmLGo2HrYcowgJqCDrhKifaz+A@mail.gmail.com>
 <20171119151350.GA23853@arthur.localdomain>
 <CA+q6zcXff34m4EskCiWdvc2BTx2J++w5gwSb43X0ejgg+sj9Wg@mail.gmail.com>
 <CAB7nPqSQFonLWsVr1OuDDd7NBHOBMNiHdvRwhxpkNV2W9-QUgg@mail.gmail.com>
 <CA+q6zcW52cJ-T3xrGm5BJ8ET6bcc0n3OYhM_oA9AQxAMZR2Otg@mail.gmail.com>
 <CA+q6zcX7W56i-k-_KK51ZQA3GZZKsFx0KzGAGm2rtC8M7948kQ@mail.gmail.com>
 <8809.1515031526@sss.pgh.pa.us>
 <CA+q6zcVuBkjWWYixH8ERPkaQiA9daAYmHTSRn=jn_Ajrzp1=Ug@mail.gmail.com>
 <20180108232959.s2ipp7tjcvlaixcs@alap3.anarazel.de>
 <846.1515629363@sss.pgh.pa.us>
 <CA+TgmoZ+eZ+RYUCr5cyoBzwXMDLZWTO264PGE81bNwwe5_WNGw@mail.gmail.com>
 <10021.1515694533@sss.pgh.pa.us>
 <CA+Tgmobvw+V3yG4LH3VzmR=9ais8fWFgeym1kYpZbjGLDzA3ig@mail.gmail.com>
Comments: In-reply-to Robert Haas <robertmhaas@gmail.com>
	message dated "Thu, 11 Jan 2018 13:30:03 -0500"
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-ID: <10982.1515695825.1@sss.pgh.pa.us>
Date: Thu, 11 Jan 2018 13:37:05 -0500
Message-ID: <10983.1515695825@sss.pgh.pa.us>
Precedence: bulk

Robert Haas <robertmhaas@gmail.com> writes:
> On Thu, Jan 11, 2018 at 1:15 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> I think you missed the point.  The question is whether the existence of a
>> subscripting function means that we need to treat the subscriptable type
>> as physically containing the subscript result type.

> I don't think I missed the point at all -- this is the exact same set
> of issues that arise with respect to functions.  Indeed, I gave an
> example of a function that needs to be updated if a column of the
> input type is altered.  In the case of functions, we've decided that
> it's not our problem.

Right, but in the case of stored arrays, we've decided that it *is*
our problem (as indeed it must be, because the user has no tools with
which they could fix a representation change for stored data).  The
question is to what extent that need would propagate to pseudo array
types.

> In other words, we're vigorously agreeing.

I think we're agreed on what should be in the v1 version of the patch.
I'm not 100% convinced that the problem won't come up eventually.

			regards, tom lane