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From "Bryan Duxbury (JIRA)" <j...@apache.org>
Subject [jira] Updated: (HBASE-19) CountingBloomFilter can overflow its storage
Date Wed, 06 Feb 2008 00:45:08 GMT

     [ https://issues.apache.org/jira/browse/HBASE-19?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Bryan Duxbury updated HBASE-19:
-------------------------------

    Fix Version/s: 0.2.0

> CountingBloomFilter can overflow its storage
> --------------------------------------------
>
>                 Key: HBASE-19
>                 URL: https://issues.apache.org/jira/browse/HBASE-19
>             Project: Hadoop HBase
>          Issue Type: Bug
>            Reporter: Stu Hood
>             Fix For: 0.2.0
>
>         Attachments: 19.patch, counting-overflow-fourbit.patch, counting-overflow-fourbit.patch,
counting-overflow.patch
>
>
> The org.onelab.filter.CountingBloomFilter implementation does not check the value of
a bucket before incrementing/decrementing it. The buckets in a Counting Bloom filter must
not be allowed to overflow, and if they reach their maximum value, they must not be allowed
to decrement. This is the only way to preserve the assumptions of the filter (without larger
buckets). See: http://en.wikipedia.org/wiki/Bloom_filter#Counting_filters
> Currently, if enough values hash to a bucket, the CountingBloomFilter may begin reporting
false negatives when it wraps back around to 0.

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