[jira] Updated: (CASSANDRA-1555) Considerations for larger bloom filters

["Stu Hood (JIRA)" <ji...@apache.org>]

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

Stu Hood updated CASSANDRA-1555:
--------------------------------

    Description: 
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.

  was:
To (optimally) support SSTables larger than 143 million keys, we need to support bloom filters larger than 2 GB, which java.util.BitSet can't handle directly.

A few options:
* Switch to a BitSet class which supports 2^63 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.


Well that's embarrassing.

> 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
>             Fix For: 0.8
>
>
> 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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