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From "Jonathan Ellis (JIRA)" <j...@apache.org>
Subject [jira] Commented: (CASSANDRA-1043) Faster UUID comparisons
Date Mon, 03 May 2010 18:51:56 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-1043?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12863470#action_12863470
] 

Jonathan Ellis commented on CASSANDRA-1043:
-------------------------------------------

we already have the JUG uuid jar in the tree, can you use that?

http://jug.safehaus.org/curr/javadoc/index.html

> Faster UUID comparisons
> -----------------------
>
>                 Key: CASSANDRA-1043
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-1043
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>            Reporter: James Golick
>            Priority: Minor
>         Attachments: faster_uuid_compare.diff, patch-v2-with-tests.diff
>
>
> As I explained on the mailing list, doing slice queries on CFs that are sorted by TimeUUIDType
gets slower as the value of count increases. According to my profiles, this is largely due
to the fact that ConcurrentSkipListMap calls the comparator very frequently, which is extremely
inefficient. In order to compare two UUIDs, it has to materialize them both in to java.util.UUID
objects which is quite slow. The more UUIDs to compare, the slower it is.
> Attached is a patch that compares UUIDs by extracting the timestamp directly from the
byte[] representation. According to my tests, it's close to a 50% performance improvement.

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