[Xapian-tickets] [Xapian] #360: SynonymPostList always requires doclength if wdf is used
Xapian
nobody at xapian.org
Fri Apr 24 01:58:21 BST 2009
#360: SynonymPostList always requires doclength if wdf is used
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Reporter: richard | Owner: olly
Type: defect | Status: new
Priority: normal | Milestone: 1.1.7
Component: Matcher | Version: SVN trunk
Severity: minor | Blockedby:
Platform: All | Blocking:
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SynonymPostList (in the opsynonym branch), currently clamps computed wdf
values to the document length. This is to ensure that the wdf does not
exceed the document length, which is a condition that some weight schemes
can rely on for computing tight bounds on the maximum weight.
It would be good to avoid having to calculate the doclength for weighting
schemes which don't require the doclength, but do require the wdf. One
approach for this would be to ensure that the wdf sum used in op synonym
only counts each physical term once; though it is hard to do this
duplicate removal in advance because query tree decay may remove some
instances of a term being used while leaving others.
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Ticket URL: <http://trac.xapian.org/ticket/360>
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