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https://issues.apache.org/jira/browse/SOLR-2906?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13153306#comment-13153306
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Yonik Seeley commented on SOLR-2906:
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bq. since wantToKeep and wantToRemove are entry counts
Yes, it seems like mixing units. But the key to understanding it is that
lastAccessed isn't a real timestamp, but just a counter that is incremented for
every access. This means that if the latest "timestamp" is 5000, and we know
we want to keep at least 1000 entries, then if we run across any timestamps
greater than 4000 that it's guaranteed to be in the top 1000 entries and we
don't need to consider it further. One can just reverse that logic to figure
out that an entry is definitely in the bottom group and we should immediately
discard it.
> Implement LFU Cache
> -------------------
>
> Key: SOLR-2906
> URL: https://issues.apache.org/jira/browse/SOLR-2906
> Project: Solr
> Issue Type: Sub-task
> Components: search
> Affects Versions: 3.4
> Reporter: Shawn Heisey
> Priority: Minor
> Attachments: ConcurrentLFUCache.java, FastLFUCache.java
>
>
> Implement an LFU (Least Frequently Used) cache as the first step towards a
> full ARC cache
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