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From "Ryan King (JIRA)" <j...@apache.org>
Subject [jira] Updated: (CASSANDRA-1555) Considerations for larger bloom filters
Date Tue, 07 Dec 2010 01:33:10 GMT

     [ https://issues.apache.org/jira/browse/CASSANDRA-1555?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Ryan King updated CASSANDRA-1555:
---------------------------------

    Attachment: CASSANDRA-1555v4.patch.gz

Another round to fix the long tests.

And on the FP rate, it seems that its actually in expected ranges based on the table here:
http://pages.cs.wisc.edu/~cao/papers/summary-cache/node8.html, though we should probably double-check
that math.

> Considerations for larger bloom filters
> ---------------------------------------
>
>                 Key: CASSANDRA-1555
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-1555
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>            Reporter: Stu Hood
>            Assignee: Ryan King
>             Fix For: 0.8
>
>         Attachments: addendum-to-1555.txt, cassandra-1555.tgz, CASSANDRA-1555v2.patch,
CASSANDRA-1555v3.patch.gz, CASSANDRA-1555v4.patch.gz
>
>
> To (optimally) support SSTables larger than 143 million keys, we need to support bloom
filters larger than 2^31 bits, which java.util.BitSet can't handle directly.
> A few options:
> * Switch to a BitSet class which supports 2^31 * 64 bits (Lucene's OpenBitSet)
> * Partition the java.util.BitSet behind our current BloomFilter
> ** Straightforward bit partitioning: bit N is in bitset N // 2^31
> ** Separate equally sized complete bloom filters for member ranges, which can be used
independently or OR'd together under memory pressure.
> All of these options require new approaches to serialization.

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