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https://issues.apache.org/jira/browse/SOLR-7689?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14588166#comment-14588166
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Yonik Seeley commented on SOLR-7689:
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bq. I think the problem would be in the query itself. If they are not immutable
now, under what conditions can they change?
The work in LUCENE-6570 is only tangentially related.
All the core Lucene queries are what I guess I would call "weakly immutable".
If the user (in this case Solr) does not change the query, then the query won't
be changed by other read / search operations and is safe to use concurrently
across different threads, etc.
So stuff like LUCENE-6570 is to make stuff like BooleanQuery truly immutable.
It would only matter to Solr in the event of a bug.
bq. The Lucene IndexSearcher calls rewrite on the query, do any queries change
internally because of a call like this?
No, they should not.
> QueryResultKey saved in cache uses the query after rewrite which causes 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
>
> 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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