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From Ivan Provalov <>
Subject Re: MLT Performance Degraded Between 4.6.1 and 5.5.2 Solr
Date Fri, 06 Jan 2017 21:09:40 GMT
After some more digging, I narrowed it down to filtering.  Without any filters, the MLT is
back to it's normal performance (8ms average response time for our case).  The issue goes
away with 6.0 upgrade. 
The hot method is Lucene's DisiPriorityQueue downHeap(), which takes 5X more calls in 5.5.2
compared to 6.0.  I am guessing that some of the Solr filters refactoring fixed it for 6.0
release.  I am not sure which.  
As a work-around, for now I just refactored the custom MLT handler to convert the filters
into boolean clauses, which takes care of the issue.  
Any insights into why this is happening in Solr 5.5.2?
 Our configuration:
1. mlt.maxqt=1002. There is an additional filter passed as a parameter3. <field name="some_mlt" type="text_en" indexed="true" stored="true" multiValued="true" omitNorms="false" termVectors="true"/>4.
text_en is a pretty standard text fieldType.

    On Monday, October 31, 2016 5:10 PM, Ivan Provalov <> wrote:

 I noticed a 3X performance degradation for MoreLikeThis between 4.6.1 and 5.5.2.  Our configuration: 
   <field name="some_mlt" type="text_en" indexed="true" stored="true" multiValued="true"
omitNorms="false" termVectors="true"/>
where text_en is a pretty standard text fieldType.
Any pointers?
Ivan Provalov

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