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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andres Freund <andres@anarazel.de>
Cc: Robert Haas <robertmhaas@gmail.com>
Cc: pgsql-hackers@postgresql.org <pgsql-hackers@postgresql.org>
Cc: Thomas Munro <thomas.munro@enterprisedb.com>
Subject: Re: Large writable variables
Date: Tue, 16 Oct 2018 13:17:02 -0400
Message-ID: <2638.1539710222@sss.pgh.pa.us> (raw)
In-Reply-To: <20181016165003.ruxut4wbxyytuhyh@alap3.anarazel.de>
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	<CA+TgmoYbL42rJbn3-fakviMurnnwS+p=rt5iXH8ccP+gQsZdMQ@mail.gmail.com>
	<20181016160612.eand666kosvv32cc@alap3.anarazel.de>
	<CA+TgmobgXaBUyVTGGusPvOUbw+zfr2pUQ9js-8+LgFoydufUeg@mail.gmail.com>
	<20181016162621.7nf2xfsl6chc7opo@alap3.anarazel.de>
	<CA+TgmoZw-JZEJacyboSJvZs28dUNhwOOTb9KUV4CVmP3UB5Gqg@mail.gmail.com>
	<20181016165003.ruxut4wbxyytuhyh@alap3.anarazel.de>

Andres Freund <andres@anarazel.de> writes:
> On 2018-10-16 12:41:44 -0400, Robert Haas wrote:
>> In terms of a function that returns both const and non-const
>> variables, it seems a bit sketchy that the caller would know what the
>> function is doing in particular cases and make decisions based on it,
>> but maybe that's just how life is.

> I don't think it's necessary the callers doing so in most cases. E.g. in
> the DestReceiver case, it'll be the choice of the testreceiver (say
> intorel_receive modifying things for DestIntoRel), not the caller
> choosing when to modify things.  The caller / users of dest receivers
> won't necessarily know.

Yeah, I think the use-case is more like "this API specifies non-const
pointers, but some instances can return pointers to const objects,
while others return non-const objects".  Changing the API to const
isn't better, it just moves where you have to cast away const.

			regards, tom lane




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