Re: RFC: list API / memory allocations

Is this a TODO?

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On Sat, Nov 19, 2011 at 12:31:09PM -0500, Stephen Frost wrote:
> Andres,
>
> * Andres Freund (andres(at)anarazel(dot)de) wrote:
> > For that I added new functions/defines which allocate all the needed memory in
> > one hunk:
> > list_immutable_make$n(),
> > List *list_new_immutable_n(NodeTag t, size_t n);
> > List *list_make_n(NodeTag t, size_t n, ...);
>
> A while back, I posted a patch to try and address this same issue. The
> approach that I took was to always pre-allocate a certain (#defined)
> amount (think it was 5 or 10 elements). There were a number of places
> that caused problems with that approach because they hacked on the list
> element structures directly (instead of using the macros/functions)-
> you'll want to watch out for those areas in any work on lists.
>
> That patch is here:
> http://archives.postgresql.org/pgsql-hackers/2011-05/msg01213.php
>
> The thread on it might also be informative.
>
> I do like your approach of being able to pass the ultimate size of the
> list in.. Perhaps the two approaches could be merged? I was able to
> make everything work with my approach, provided all the callers used the
> list API (I did that by making sure the links, etc, actually pointed to
> the right places in the pre-allocated array). One downside was that the
> size ended up being larger that it might have been in some cases.
>
> Thanks,
>
> Stephen

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Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

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