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https://issues.apache.org/jira/browse/SOLR-7689?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14589929#comment-14589929
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Yonik Seeley commented on SOLR-7689:
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bq. The normal pattern is a little different here because we need to return the
re-written query wrapped in a ReRankQuery in order to preserver the re-rank
Explain.
But that is the normal pattern of how rewrite() is implemented.
bq. The only trick to this is that the cloned ReRankQuery will also have
rewrite() called on it because of the loop in IndexSearcher.rewrite()
This isn't a problem if you follow the normal pattern of returning a clone
*only if* one of your sub-queries was changed by the rewrite. The query will
change the first time through the loop and won't change the second time.
> ReRankQuery rewrite method can change the QueryResultKey causing cache misses.
> ------------------------------------------------------------------------------
>
> Key: SOLR-7689
> URL: https://issues.apache.org/jira/browse/SOLR-7689
> Project: Solr
> Issue Type: Bug
> Components: search, SearchComponents - other
> Reporter: Emad Nashed
> Assignee: Joel Bernstein
> Attachments: SOLR-7689.patch, SOLR-7689.patch, SOLR-7689.patch
>
>
> 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.
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