[SOLR-7689] ReRankQuery rewrite method can change the QueryResultKey causing cache misses.

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 5.2.2, 6.0
• Component/s: search, SearchComponents - other
• Assignee: Joel Bernstein
• Reporter: Emad Nashed
• Created: 16/Jun/15 06:53
• Updated: 09/May/16 18:47
• Resolved: 18/Sep/15 02:09

Description

In SolrIndexSearcher class, the key used to lookup results in queryResultCache uses the original query.

However later in createNormalizedWeight the query gets re-written, and then saved in the queryResultCache after it's re-written.

This causes cache misses for the same query, and un-necessary inserts in the queryResultCache.

I can reproduce this using a re-ranking query that is using a main query as a dismax query, the dismax Query could be re-written into a TermQuery, which makes sense, but will cause cache misses.

I tested a quick solution by just using q.clone() when it comes to build QueryResultKey, and it works fine, but not sure if that is the best way of doing it.