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From "T Jake Luciani (JIRA)" <j...@apache.org>
Subject [jira] Commented: (CASSANDRA-1555) Considerations for larger bloom filters
Date Thu, 23 Dec 2010 21:57:46 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-1555?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12974761#action_12974761
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T Jake Luciani commented on CASSANDRA-1555:
-------------------------------------------

The CFMetadata -> SSTableReader change is required because the Descriptor is part of the
SSTableReader only and the Descriptor is where we know what type of bloom filter its using.
 See SSTableNamesIterator.read()

> 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: 0.7.1
>
>         Attachments: 1555-v7.txt, 1555_v5.txt, 1555_v6.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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