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https://issues.apache.org/jira/browse/CASSANDRA-1043?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12863405#action_12863405
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James Golick commented on CASSANDRA-1043:
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Sylvain, you're right about hi & 0x0FFF. Full disclosure: I'm not a UUID expert
either.
You're also probably right that we can remove the subtraction and division from
the end. I don't see any harm in that, since it's only really there for
creating a timestamp that can be converted in to a Date object of some kind.
I'm working on some unit tests to make sure this works as expected...
> 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
>
>
> 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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