Re: POC: converting Lists into arrays

I wrote:
> [ list_qsort-API-change.patch ]

Also, here's a follow-on patch that cleans up some crufty code in
heap.c and relcache.c to use list_qsort, rather than manually doing
insertions into a list that's kept ordered. The existing comments
argue that that's faster than qsort for small N, but I think that's
a bit questionable. And anyway, that code is definitely O(N^2) if
N isn't so small, while this replacement logic is O(N log N).

This incidentally removes the only two calls of lappend_cell_oid.
There are no callers of lappend_cell_int, and only one of lappend_cell,
and that one would be noticeably cleaner if it were rewritten to use
list_insert_nth instead. So I'm a bit tempted to do so and then nuke
all three of those functions, which would at least make some tiny dent
in Andres' unhappiness with the messiness of the List API. Thoughts?

regards, tom lane