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Re: [PATCH] unified frontend support for pg_malloc et al and palloc/pfree mulation (was xlogreader-v4)

From: Andres Freund <andres(at)anarazel(dot)de>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Heikki Linnakangas <hlinnakangas(at)vmware(dot)com>,pgsql-hackers(at)postgresql(dot)org
Subject: Re: [PATCH] unified frontend support for pg_malloc et al and palloc/pfree mulation (was xlogreader-v4)
Date: 2013-01-09 16:42:33
Message-ID: 20130109164233.GA11725@awork2.anarazel.de (view raw or flat)
Thread:
Lists: pgsql-hackers
On 2013-01-09 11:37:46 -0500, Tom Lane wrote:
> Andres Freund <andres(at)2ndquadrant(dot)com> writes:
> > On 2013-01-09 13:46:53 +0200, Heikki Linnakangas wrote:
> >> I don't understand the need for this change. Can't you just:
> >> #define palloc(s) pg_malloc(s)
> >> in the frontend context?
>
> > Yes, that would be possible, but imo its the inferior solution:
>
> I'm with Heikki: in fact, I will go farther and say that this approach
> is DOA.  The only way you get to change the backend's definition of
> palloc is if you can show that doing so yields a performance boost
> in the backend.  Otherwise, we use a macro or whatever is necessary
> to allow frontend code to have a different underlying implementation
> of palloc(x).

Whats the usecase for being able to redefine it after the patch? Its not
like you can do anything interesting given that pfree() et. al. is not a
macro.

> > * removing allows us to get rid of the following ugliness in dirmod.c:
>
> I agree that what dirmod is doing is pretty ugly, but it's localized
> enough that I don't care particularly.  (Really, the only reason it's
> a hack and not The Solution is that at the moment there's only one
> file doing it that way.  A trampoline function for use only by code
> that needs to work in both frontend and backend isn't an unreasonable
> idea.)

Well, after the patch the trampoline function would be palloc() itself.

Greetings,

Andres Freund


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Next:From: Peter GeogheganDate: 2013-01-09 16:47:35
Subject: Re: [PATCH 1/2] Provide a common malloc wrappers and palloc et al. emulation for frontend'ish environs
Previous:From: Magnus HaganderDate: 2013-01-09 16:37:59
Subject: Re: [PATCH] Patch to fix missing libecpg_compat.lib and libpgtypes.lib.

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