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From Shawn Heisey <apa...@elyograg.org>
Subject Re: Different order of docs between SOLR-4.10.4 to SOLR-6.5.1
Date Fri, 04 Aug 2017 12:52:26 GMT
On 8/4/2017 1:02 AM, SOLR4189 wrote:
> I need to upgrade from SOLR-4.10.3 to SOLR-6.5.1 in production environment. 
> When I checked it in the test environment, I noticed the order of returned docs for each
query is different. The score has changed as well. I use same similarity algorithm - OccapiBM25
as in previous version. Number of shards and number of docs by shards also haven't changed.

You're comparing versions released more than two years apart, and across
two major version upgrades.

Solr is an application built around Lucene.  The score calculation in
Lucene is frequently tweaked, producing slightly different results even
with identical data.  Over such a large version discrepancy, I would be
very surprised if the order and the scores were the same.

Is the index identical between the versions?  If the indexes were each
built from scratch by their respective versions, rather than going
through an index upgrade procedure, they are very likely NOT completely
identical.  Text analysis components are also tweaked frequently, to fix
bugs and improve behavior.

If the shard hash ranges are not the same on the old and new versions,
that could contribute to differences in scoring as well.

Are you writing because you're seeing different results, or because you
think the order you're seeing in the newer version is wrong?

Thanks,
Shawn


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