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From "Stu Hood (JIRA)" <j...@apache.org>
Subject [jira] Updated: (HADOOP-2654) CountingBloomFilter can overflow its storage
Date Sat, 19 Jan 2008 07:54:34 GMT

     [ https://issues.apache.org/jira/browse/HADOOP-2654?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Stu Hood updated HADOOP-2654:

    Attachment: counting-overflow-fourbit.patch

Use (long[]).clone() rather than Arrays.copyOf.

> CountingBloomFilter can overflow its storage
> --------------------------------------------
>                 Key: HADOOP-2654
>                 URL: https://issues.apache.org/jira/browse/HADOOP-2654
>             Project: Hadoop
>          Issue Type: Bug
>          Components: contrib/hbase
>            Reporter: Stu Hood
>         Attachments: counting-overflow-fourbit.patch, counting-overflow-fourbit.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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