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From "Marcus Eriksson (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-14160) maxPurgeableTimestamp should traverse tables in order of minTimestamp
Date Tue, 17 Apr 2018 14:00:00 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-14160?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16440885#comment-16440885
] 

Marcus Eriksson commented on CASSANDRA-14160:
---------------------------------------------

hey [~josnyder] the code looks good to me, but, as [~jjirsa] mentioned above, a unit test
that makes sure the sstables are returned in the correct order should be added. You also mentioned
a that you had not yet benchmarked the change, have you done that? If not, that would also
be nice.

> 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
>            Priority: Major
>              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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