[Xapian-tickets] [Xapian] #304: Calculate LHS weight earlier in AND_MAYBE to avoid calling RHS in some cases

[Xapian]

#304: Calculate LHS weight earlier in AND_MAYBE to avoid calling RHS in some
cases
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 Reporter:  richard      |        Owner:  olly    
     Type:  enhancement  |       Status:  new     
 Priority:  normal       |    Milestone:          
Component:  Matcher      |      Version:  SVN HEAD
 Severity:  normal       |   Resolution:          
 Keywords:               |    Blockedby:          
 Platform:  All          |     Blocking:          
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Comment(by olly):

 Since the tighter bound only applies to the current docid, we can't do
 most of our optimisations based on it.

 This new "skip_to2" method seems to have the semantics:

 {{{skip_to2(did, min_wt)}}} advances to docid {{{did}}} if that document
 is in this posting list and has weight at least {{{min_wt}}}.  Otherwise
 it advances to the first document in the posting list with document id >
 {{{did}}}.

 We can't advance beyond the document after {{{did}}} since that document
 might require a lower minimum weight contribution than {{{min_wt}}}.

 What optimisation(s) does this actually allow?  I'm failing to see much
 gain here...

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Ticket URL: <http://trac.xapian.org/ticket/304#comment:1>
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