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From Yanick Gamelin <yanick.game...@ericsson.com>
Subject Lucene scoring and random result order
Date Thu, 25 Aug 2011 19:02:26 GMT
Hi all,

I have the following problem with Lucene being not deterministic.

I use a MultiSearcher to process a search and when I get hits with same score, those are returned
in a random order.
I wouldn't care much about the order of the hits with same score if I could get them all,
so I could sort them myself.
But if we request a maximum number of results lower than the amount of hits with same score,
we only get a subset of those hits and that result list of hits will change because the order
is not guarantied.
Sometimes the first part of the result list is consistent because scoring is different for
those hits, but then we have a bit block with equals scoring, so Lucene only take what it
need to fill the rest of the list. Lucene takes randomly what its need from the big block
of equal score

As an example imagine x,y,and z which have a high scoring, all other letters have same score
3 consecutive searches will give
[x,y,z,a,b,c,d,f,g,h,i,j]
[x,y,z,q,w,e,r,t,u,i,o,p]
[x,y,z,m,n,b,v,c,a,s,d,g]

Pretty annoying eh? So, what can I do about that?

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