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https://issues.apache.org/jira/browse/LUCENE-8213?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16404005#comment-16404005
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Amir Hadadi commented on LUCENE-8213:
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"It causes a latency hit regardless"
I will clarify the issue. Assume you have these queries:
q1: term query that matches 1 doc
q2: range query that matches 10M docs
And you query for "q1 AND q2"
q2 would be an IndexOrDocValuesQuery and would use doc values to do a range
check on the single doc that matches q1, so the BKD tree won't be scanned for
10M documents.
However, when q2 gets cached, the bit set for the entire 10M docs is cached,
which causes "q1 AND q2" to suddenly spike in latency.
> offload caching to a dedicated threadpool
> -----------------------------------------
>
> Key: LUCENE-8213
> URL: https://issues.apache.org/jira/browse/LUCENE-8213
> Project: Lucene - Core
> Issue Type: Improvement
> Components: core/query/scoring
> Affects Versions: 7.2.1
> Reporter: Amir Hadadi
> Priority: Minor
> Labels: performance
>
> IndexOrDocValuesQuery allows to combine non selective range queries with a
> selective lead iterator in an optimized way. However, the range query at some
> point gets cached by a querying thread in LRUQueryCache, which negates the
> optimization of IndexOrDocValuesQuery for that specific query.
> It would be nice to see a caching implementation that offloads to a different
> thread pool, so that queries involving IndexOrDocValuesQuery would have
> consistent performance characteristics.
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