[Xapian-tickets] [Xapian] #307: OP_SYNONYM should allow field weights to be set on its members

[Xapian]

#307: OP_SYNONYM should allow field weights to be set on its members
-------------------------+--------------------------------------------------
 Reporter:  richard      |       Owner:  richard  
     Type:  enhancement  |      Status:  assigned 
 Priority:  normal       |   Milestone:  1.1.1    
Component:  Matcher      |     Version:  SVN trunk
 Severity:  normal       |    Keywords:           
Blockedby:               |    Platform:  All      
 Blocking:               |  
-------------------------+--------------------------------------------------
Changes (by richard):

  * blockedby:  50 =>


Comment:

 That potential fix would be done internally, though - the thinking behind
 this ticket was really to provide an API to allow OP_SYNONYM to more
 closely follow what would happen if you performed the synonym expansion at
 index time in a system with wdf multipliers for each field (as in omega),
 but allowing the relative weighting of fields to be adjusted at search
 time instead of index time.  I don't have a concrete example of wanting to
 use it in this way, though - it was just a feeling that it would be nice
 to be "feature complete" here.

 I think if the multipliers are in the range (0,1] this wouldn't work well;
 if you wanted term "title:A" to have 5 times the wdf of term "body:B",
 you'd implement that by dividing the wdfs of "body:B" by 5 and you'd lose
 any distinction between documents with fairly different values (eg, 1 and
 5) for the wdf of "body:B".

 An alternative approach to making one field more important is to use a OR
 query instead of a synonym query.  The weightings which come out of doing
 that are different, of course (that's the point of OP_SYNONYM), but you
 could use an OP_SYNONYM as the main query, and an OR query with a fairly
 low multiplier to give a slight boost to a particular field, if you really
 needed to adjust the weight in this sort of way.

 I think we're both agreed the WONTFIX is an appropriate response, given
 the difficulty of coming up with a reasonable implementation, and given
 the lack of definite use for this.  Closing as that.

-- 
Ticket URL: <http://trac.xapian.org/ticket/307#comment:11>
Xapian <http://xapian.org/>
Xapian