Plan time Improvement - 64bit bitmapset

Hi,

While analyzing some complex query and switching away from using the
materialized views to their underlying ones I got interested in the long
plan times (minutes and up) and did some profiling work.

The queries are high dimensional star-schema-alike queries 
(unfortunately quite private (health) data and a schema I may not make 
public).

Using oprofile and
"valgrind --tool=callgrind --dump-instr=yes --collect-jumps=yes
--simulate-cache=yes --simulate-hwpref=yes" I found that one of the 
bitmapset functions are near the top of the profile.

When switching bitmapword and companions in bitmap.h to u64 and s64 
respectively I get an improvement up to 15% in queries with 16+ joins. 
The more joins the bigger the win.

In the very simple (structurally) query with 16 joins the improvement is 
around 1-2%.
With the most complex query I tested (the nr. of participating relations 
is hard to count because of many views) I get an improvement up to 15%.
I did not test with bigger/more complex queries because it got too slow 
to get sufficiently thorough results.

When playing around with join_collapse_limit, from_collapse_limit, geqo, 
geqo_threshold I found that unless the settings are set to really low 
values I can find performance improvements for most combinations.

I could not find any regression in the queries we use - and I can't see 
where there would be a significant overhead.

Unfortunately the more interesting trace seems to be the valgrind one - 
which with these options currently only "kcachegrind" can read. I could 
not get a usable text export out of the latter.

Linked are two overview pictures before (32bit.png) and after 
(64bit.png) the switch to using 64bit bitmapsets from the backend 
evaluating a complex query once:

http://anarazel.de/pg/32bit_bitmapsets.png
http://anarazel.de/pg/64bit_bitmapsets.png

That seems like an easy change - is there a reason not to do this if the 
arch is a 64bit one?

Can anybody else with complex queries test my results? (I can provide a 
patch if wanted).

Andres

PS: If kcachegrind users want to see the trace, speak up...