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From "Benedict (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-8730) Optimize UUIDType comparisons
Date Thu, 05 Mar 2015 11:08:38 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-8730?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14348607#comment-14348607
] 

Benedict commented on CASSANDRA-8730:
-------------------------------------

bq. UUIDType is supposed to correctly compare TimeUUIDTypes

Regrettably, no it isn't. It actually has a different comparison logic for the LSB of the
TimeUUID.

bq. What is UUIDTypeTest.permute used to check for?

I've commented this method now, but it is to exhaustively check each of the permutations of
any given comparison point (i.e. each byte for all but the byte containing the UUID type,
and the top 4 bits only for that byte). I've also updated the tests to randomise the input
to the permutations, although logically this should have no impact.

bq. Maybe resurrect the old versions to check that they are prior version consistent in the
unit tests. Maybe modify the test to use a seeded RNG with a known seed and print it out so
if there is a failure we can reproduce.

Sure, added to branch.

> Optimize UUIDType comparisons
> -----------------------------
>
>                 Key: CASSANDRA-8730
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-8730
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: J.B. Langston
>            Assignee: Benedict
>             Fix For: 3.0
>
>
> Compaction is slow on tables using compound keys containing UUIDs due to being CPU bound
by key comparison.  [~benedict] said he sees some easy optimizations that could be made for
UUID comparison.



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