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

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