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https://issues.apache.org/jira/browse/CASSANDRA-19497?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17894922#comment-17894922
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Caleb Rackliffe commented on CASSANDRA-19497:
---------------------------------------------
Attached two more flamegraphs to document the overhead of all the non-batched
single-partition reads: [^cpu-trunk.html] [^alloc-trunk.html]
> ResultRetriever should batch clusterings/rows during SAI post-filtering reads
> -----------------------------------------------------------------------------
>
> Key: CASSANDRA-19497
> URL: https://issues.apache.org/jira/browse/CASSANDRA-19497
> Project: Cassandra
> Issue Type: Improvement
> Components: Feature/SAI
> Reporter: Caleb Rackliffe
> Assignee: Caleb Rackliffe
> Priority: Normal
> Fix For: 5.0.x, 5.x
>
> Attachments: alloc-trunk.html, cpu-trunk.html, heap-flamegraph.html,
> wall-no-parked-threads.html
>
> Time Spent: 10m
> Remaining Estimate: 0h
>
> SAI currently creates and executes a {{SinglePartitionReadCommand}} for every
> {{PrimaryKey}} the index produces to read the corresponding row for
> post-filtering. Informed by the limits present in the read command itself, it
> should be possible to batch those reads w/ a {{ClusteringIndexNamesFilter}}
> in many fewer {{SinglePartitionReadCommands}}. When we have a handful of
> matches in a large partition, this seems like would involve many fewer seeks,
> less unnecessary object creation, etc.
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