Horton

Re: Pre-alloc ListCell's optimization

Greg Stark <gsstark@mit.edu>

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From: Greg Stark <gsstark@mit.edu>
To: Stephen Frost <sfrost@snowman.net>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, Alvaro Herrera <alvherre@commandprompt.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2011-05-27T03:58:58Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Replace the parser's namespace tree (which formerly had the same

  2. Turns out that my recent elimination of the 'redundant' flatten_andors()

On Thu, May 26, 2011 at 8:52 PM, Stephen Frost <sfrost@snowman.net> wrote:
>  list_concat() does explicitly say that cells will
> be shared afterwards and that you can't pfree() either list (note that
> there's actually a couple cases currently that I discovered which were
> also addressed in the original patch where I commented out those
> pfree()'s).

So in traditional list it would splice the second argument onto the
end of the first list. This has a few effects that it sounds like you
haven't preserved. For example if I insert an element anywhere in
list2 -- including in the first few elements -- it's also inserted
into list1.

I'm not really sure we care about these semantics with our lists
though. It's not like they're supposed to be a full-featured lisp
emulator and it's not like the C code pulls any particularly clever
tricks with lists. I suspect we may have already broken these
semantics long ago but I haven't looked to see if that's the case.




-- 
greg