Solr more like this don't return score while specify `mlt.count`

Question

I'm using solr's more like this to analyze the most similar documents. But while I specify mlt.count argument and if it is not 15, the score don't show. The more like this arguments is mlt=true&mlt.fl=text&mlt.count=12, while text is the filed that has term vector. And the fl argument is *,score. I queried this url:

http://localhost:8983/solr/collection1/select?q=id%3A1967956383&wt=json&indent=true&mlt=true&mlt.fl=text&mlt.count=12.

When I specify mlt.count=15, the score shows up. And after that, I query mlt.count=12 again, it shows up, too.

My solr version is 4.0.

Does anybody have any idea? Thanks!

Answer 1

This has been documented as a SOLR bug SOLR-5042, and a patch posted against solr version 4.3. I've relocated that patch back to 4.2.1 and seen that it fixes this behavior there.

If you query the /mlt handler directly, instead of using the mlt component under the /select handler, you can work around this issue, as the handler accepts its count as rows=12 instead of mlt.count=12.