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https://issues.apache.org/jira/browse/LUCENE-9002?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17397340#comment-17397340
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ASF subversion and git services commented on LUCENE-9002:
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Commit 2e3620fe0a70d7e1dc3261112ea314ab5512bd3f in lucene-solr's branch
refs/heads/branch_8x from Julie Tibshirani
[ https://gitbox.apache.org/repos/asf?p=lucene-solr.git;h=2e3620f ]
LUCENE-10043: Decrease default LRUQueryCache#skipCacheFactor to 10
In LUCENE-9002 we introduced logic to skip caching a clause if it would be too
expensive compared to the usual query cost. Specifically, we avoid caching a
clause if its cost is estimated to be a 250x higher than the lead iterator's.
We've found that the default of 250 is quite high and can lead to poor tail
latencies. This PR decreases it to 10 to cache more conservatively
> query caching leads to absurdly slow queries
> --------------------------------------------
>
> Key: LUCENE-9002
> URL: https://issues.apache.org/jira/browse/LUCENE-9002
> Project: Lucene - Core
> Issue Type: Improvement
> Components: core/search
> Affects Versions: 7.7.2, 8.2
> Reporter: Guoqiang Jiang
> Priority: Major
> Labels: cache, performance
> Time Spent: 9h 20m
> Remaining Estimate: 0h
>
> *Description*
> We have dozens of ES clusters(based on Lucene) for metric scenarios. Most of
> the queries are like this: _host_ip:10.10.10.10 AND timestamp:[2019-10-01
> 00:00:00 TO 2019-10-05 23:59:59]_. And we frequently encounter some absurdly
> slow queries.
> *Solution*
> For a long time range query(e.g. 5 days), each range query will consume tens
> of megabytes of memory and spend hundreds of milliseconds to cache, but the
> benefits are not obvious. And those large cache entries will cause frequent
> cache eviction. So it's better to skip the caching action directly when
> large range query appears with a selective lead iterator.
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