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https://issues.apache.org/jira/browse/SOLR-3393?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13261098#comment-13261098
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Shawn Heisey commented on SOLR-3393:
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Further work, but no patch yet because it requires a bunch of test tweaks: I
have split timeDecay into evictDecay and warmDecay. The timeDecay option still
works, and sets both to true. In the absence of the timeDecay option, I've
made evictDecay default to false and warmDecay default to true.
In order to cause elements to decay over time, every entry in the cache must be
removed from one LinkedHashSet and added to another. This is probably pretty
fast for this implementation, but it does still require time. My use case
scenario will have commits relatively often, up to once a minute. For me,
doing the decay at warm time is enough, and results in fewer items to touch.
To have it happen at eviction time is overhead I don't need, but it would be
correct for some use cases. What are some other people's opinions about the
default settings?
> Implement an optimized LFUCache
> -------------------------------
>
> Key: SOLR-3393
> URL: https://issues.apache.org/jira/browse/SOLR-3393
> Project: Solr
> Issue Type: Improvement
> Components: search
> Affects Versions: 3.6, 4.0
> Reporter: Shawn Heisey
> Priority: Minor
> Fix For: 4.0
>
> Attachments: SOLR-3393.patch, SOLR-3393.patch
>
>
> SOLR-2906 gave us an inefficient LFU cache modeled on
> FastLRUCache/ConcurrentLRUCache. It could use some serious improvement. The
> following project includes an Apache 2.0 licensed O(1) implementation. The
> second link is the paper (PDF warning) it was based on:
> https://github.com/chirino/hawtdb
> http://dhruvbird.com/lfu.pdf
> Using this project and paper, I will attempt to make a new O(1) cache called
> FastLFUCache that is modeled on LRUCache.java. This will (for now) leave the
> existing LFUCache/ConcurrentLFUCache implementation in place.
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