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From "Josh Snyder (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-14160) maxPurgeableTimestamp should traverse tables in order of minTimestamp
Date Sun, 14 Jan 2018 00:55:00 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-14160?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16325397#comment-16325397
] 

Josh Snyder commented on CASSANDRA-14160:
-----------------------------------------

I believe I've now fixed the issues. Take a look at:

https://github.com/hashbrowncipher/cassandra/tree/cassandra-14160
https://circleci.com/gh/hashbrowncipher/cassandra/2

> 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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