- Update to 1.4.1
* Constructing a Query for a non-reference counted PostingSource object will
now try to clone the PostingSource object (as happened in 1.3.4 and
earlier). This clone code was removed as part of the changes in 1.3.5 to
support optional reference counting of PostingSource objects, but that breaks
the case when the PostingSource object is on the stack and goes out of scope
before the Query object is used. Issue reported by Till Schäfer and analysed
by Daniel Vrátil in a bug report against Akonadi:
https://bugs.kde.org/show_bug.cgi?id=363741
* Add BM25PlusWeight class implementing the BM25+ weighting scheme, implemented
by Vivek Pal (https://github.com/xapian/xapian/pull/104).
* Add PL2PlusWeight class implementing the PL2+ weighting scheme, implemented
by Vivek Pal (https://github.com/xapian/xapian/pull/108).
* LMWeight: Implement Dir+ weighting scheme as DIRICHLET_PLUS_SMOOTHING.
Patch from Vivek Pal.
* Add CoordWeight class implementing coordinate matching. This can be useful
for specialised uses - e.g. to implement sorting by the number of matching
filters.
* DLHWeight,DPHWeight,PL2Weight: With these weighting schemes, the formulae
can give a negative weight contribution for a term in extreme cases. We
used to try to handle this by calculating a per-term lower bound on the
contribution and subtracting this from the contribution, but this idea
is fundamentally flawed as the total offset it adds to a document depends on
what combination of terms that document matches, meaning in general the
offset isn't the same for every matching document. So instead we now clamp
each term's weight contribution to be >= 0.
* TfIdfWeight: Always scale term weight by wqf - this seems the logical
approach as it matches the weighting we'd get if we weighted every non-unique
term in the query, as well as being explicit in the Piv+ formula.
OBS-URL: https://build.opensuse.org/request/show/439920
OBS-URL: https://build.opensuse.org/package/show/server:search/xapian-core?expand=0&rev=72
