Xapian discuss - Sep 2011 - Tryout paches for faster chert search: http://trac.xapian.org/ticket/326

Hi,

w.r.t. http://trac.xapian.org/ticket/326

I'd like to try out some of the patches mentioned against my xapian svn
trunk
to see what kind of improvement can be realised.

There are quite a few patches, so can I simply try them all top-to-bottom, or
which of them are recommended (ie, I don't want to screw with the index
format)?

Thanks
h

I've had a stab at applying some of the patches, here's some feedback:

small_doclen_chunks.patch
Tested searching on a 161GB test index (which is comprised of 40 sub-indexes):
Avg search time goes from about 0m7.226s to about 0m7.188s.
So a marginal speedup.

avoid_string_appends_1.patch fails - chert_utils.h no longer exists.  I
searched around in the commit emails, but things have clearly changed a bit.

avoid_string_appends_and_loop_unroll_2.patch - ditto

avoid_string_operations.patch - ditto

optimise_unpack_uint.patch - ditto

chunktypes.patch
Code in trunk has changed quite a bit where this patch touches - I started
massaging things based on the *.cc.rej files, but things have evolved quite a
bit, and my lack of intimate knowledge of xapian/backend/chert internals has
me stumped.

I'm keen to try chunktypes.patch, since it's potential seems quite
significant.  I have about 2TB total indexes to play with (segmented into
various chunk sizes) so it may be interesting to see how it performs.

optimise_unpack_uint.patch also seems to promise a speed-up worth pursuing.

I'd love to try all the patches out to see what the total gains are (and
will
report them here), but need help with massaging the patches a bit.  Richard,
since you are the original author of ticket #326 and the patches, could I beg
your assistance?

h