On Thu, Aug 10, 2017 at 1:39 AM, Thomas Munro
<thomas.mu...@enterprisedb.com> wrote:
> On my computer it took ~1.5 seconds to plan a 1000 partition join,
> ~7.1 seconds to plan a 2000 partition join, and ~50 seconds to plan a
> 4000 partition join.  I poked around in a profiler a bit and saw that
> for the 2000 partition case I spent almost half the time in
> create_plan->...->prepare_sort_from_pathkeys->find_ec_member_for_tle,
> and about half of that was in bms_is_subset.  The other half the time
> was in query_planner->make_one_rel which spent 2/3 of its time in
> set_rel_size->add_child_rel_equivalences->bms_overlap and the other
> 1/3 in standard_join_search.

Ashutosh asked me how I did that.  Please see attached. I was
explaining simple joins like SELECT * FROM foofoo JOIN barbar USING
(a, b).  Here also is the experimental hack I tried when I saw
bitmapset.c eating my CPU.

Thomas Munro

Attachment: bitmapset-track-leading-empty-space.patch
Description: Binary data

Attachment: make-partitions.sh
Description: Bourne shell script

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