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From "Jeff Jirsa (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-14160) maxPurgeableTimestamp should traverse tables in order of minTimestamp
Date Sat, 13 Jan 2018 00:55:16 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-14160?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16324826#comment-16324826
] 

Jeff Jirsa commented on CASSANDRA-14160:
----------------------------------------

Hey [~josnyder], the code looks sane, but it also doesn't compile (or rather, the existing
unit tests for the {{OverlapIterator}} no longer compile). Any chance you can address that?


> maxPurgeableTimestamp should traverse tables in order of minTimestamp
> ---------------------------------------------------------------------
>
>                 Key: CASSANDRA-14160
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-14160
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Compaction
>            Reporter: Josh Snyder
>            Assignee: Josh Snyder
>              Labels: performance
>             Fix For: 4.x
>
>
> In maxPurgeableTimestamp, we iterate over the bloom filters of each overlapping SSTable.
Of the bloom filter hits, we take the SSTable with the lowest minTimestamp. If we kept the
SSTables in sorted order of minTimestamp, then we could short-circuit the operation at the
first bloom filter hit, reducing cache pressure (or worse, I/O) and CPU time.
> I've written (but not yet benchmarked) [some code|https://github.com/hashbrowncipher/cassandra/commit/29859a4a2e617f6775be49448858bc59fdafab44]
to demonstrate this possibility.



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