When grouping the results of a query with group.query there is a ClassCastException in org.apache.solr.search.Grouping.CommandQuery.finish (line 890) since the collector is wrapped in a MultiCollector.
The wanted topCollector is available in the inner class so it can be used directly and the cast is not necessary at all. After that change there are still the scores missing in the result, so populating the scores is necessary, too.
I will create a PR showing the error and also containing a fix.
- is caused by
LUCENE-8405 Remove TopHits.maxScore
- is duplicated by
SOLR-13906 ClassCastException in Group Sort when 'score' field in fl
- links to