Date: Tue, 19 Sep 2017 11:21:43 +0300
From: Arthur Zakirov <a.zakirov@postgrespro.ru>
To: Dmitry Dolgov <9erthalion6@gmail.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, David Steele <david@pgmasters.net>,
	Peter Eisentraut <peter.eisentraut@2ndquadrant.com>,
	PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: [PATCH] Generic type subscripting
Message-ID: <20170919082141.GA2647@zakirov.localdomain>
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On Mon, Sep 18, 2017 at 12:25:04PM +0200, Dmitry Dolgov wrote:
> > I think it would be good to add new catalog table. It may be named as
> pg_type_sbs or pg_subscripting (second is better I think).
> > This table may have the fields:
> > - oid
> > - sbstype
> > - sbsinit
> > - sbsfetch
> > - sbsassign
> 
> What is `sbstype`?

'sbstype' is oid of type from pg_type for which subscripting is created. I.e. pg_type may not have the 'typsubsparse' field.

> > And command 'CREATE SUBSCRIPTING' should add an entry to the
> pg_subscripting table. It also adds entries to the pg_depend table:
> dependency between pg_type and pg_subscripting, dependency between pg_type
> and pg_proc.
> > 'DROP SUBSCRIPTING' should drop this entries, it should not drop init
> function.
> 
> Why we should keep those subscripting functions? From my understanding
> they're
> totally internal and useless without subscripting context.
> 

Other similar commands do not drop related functions. For example 'DROP CAST' do not drop a function used to perform a cast.

> It also adds entries to the pg_depend table: dependency between pg_type and pg_subscripting, dependency between pg_type and pg_proc.

Here was a typo from me. Last entry is dependency between pg_subscripting and pg_proc.

-- 
Arthur Zakirov
Postgres Professional: http://www.postgrespro.com
Russian Postgres Company


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