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From "Jonathan Ellis (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-2975) Upgrade MurmurHash to version 3
Date Sat, 30 Jul 2011 16:06:09 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-2975?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13073213#comment-13073213
] 

Jonathan Ellis commented on CASSANDRA-2975:
-------------------------------------------

Also, it's not quite as simple as ripping out M2 and replacing with M3 -- we need to continue
to support M2 for compatibility with old data files.  Look at uses of Descriptor.hasStringsInBloomFilter
for a similar change.

> Upgrade MurmurHash to version 3
> -------------------------------
>
>                 Key: CASSANDRA-2975
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-2975
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>    Affects Versions: 0.8.3
>            Reporter: Brian Lindauer
>            Priority: Trivial
>              Labels: lhf
>
> MurmurHash version 3 was finalized on June 3. It provides an enormous speedup and increased
robustness over version 2, which is implemented in Cassandra. Information here:
> http://code.google.com/p/smhasher/
> The reference implementation is here:
> http://code.google.com/p/smhasher/source/browse/trunk/MurmurHash3.cpp?spec=svn136&r=136
> I have already done the work to port the (public domain) reference implementation to
Java in the MurmurHash class and updated the BloomFilter class to use the new implementation:
> https://github.com/lindauer/cassandra/commit/cea6068a4a3e5d7d9509335394f9ef3350d37e93
> Apart from the faster hash time, the new version only requires one call to hash() rather
than 2, since it returns 128 bits of hash instead of 64.

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