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https://issues.apache.org/jira/browse/CASSANDRA-20668?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Caleb Rackliffe updated CASSANDRA-20668:
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Status: Ready to Commit (was: Review In Progress)
> SAI range queries can spend too much time in
> TrieMemoryIndex$Collector#updateLastQueueSize() doing unproductive work
> ---------------------------------------------------------------------------------------------------------------------
>
> Key: CASSANDRA-20668
> URL: https://issues.apache.org/jira/browse/CASSANDRA-20668
> Project: Apache Cassandra
> Issue Type: Improvement
> Components: Feature/SAI
> Reporter: Caleb Rackliffe
> Assignee: Caleb Rackliffe
> Priority: Normal
> Fix For: 5.0.x, 5.x
>
> Attachments: ci_summary.html,
> e20ea330-3519-11f0-912e-31b7d282b812-flamegraph.html, result_details.tar.gz,
> screenshot_2025-05-20_at_9.04.57___pm_720.png,
> screenshot_2025-05-20_at_9.05.15___pm_720.png
>
> Time Spent: 10m
> Remaining Estimate: 0h
>
> {{TrieMemoryIndex}} performs range queries by traversing the in-memory trie,
> finding the terms in the range, and adding the primary keys for each term to
> a priority queue (because they need to be in order). At one point, to make
> sure we didn't have an issue with the priority queue's backing array being
> constantly resized for large ranges, we started tracking the last queue size
> to reuse it when creating a new {{Collector}} for the query. In some recent
> performance testing, we've seen up to 10% of samples in a CPU flame graph
> (attached) in {{updateLastQueueSize()}}, which needs to be addressed.
> The naïve question here is, of course, why the priority queue itself isn't
> thread local. There are also some usages of lambdas and other
> micro-optimizations that might be possible...
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