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From "Jonathan Ellis (JIRA)" <j...@apache.org>
Subject [jira] Commented: (CASSANDRA-790) SSTables limited to (2^31)/15 keys
Date Fri, 12 Feb 2010 22:42:28 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-790?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12833212#action_12833212
] 

Jonathan Ellis commented on CASSANDRA-790:
------------------------------------------

rather than just cap the filter size, you need to reduce bucketsPerElement too or you will
get suboptimal number-of-hashes calculation, since you haven't told it it can't have as big
a filter as it wanted.

> SSTables limited to (2^31)/15 keys
> ----------------------------------
>
>                 Key: CASSANDRA-790
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-790
>             Project: Cassandra
>          Issue Type: Bug
>    Affects Versions: 0.5, 0.6, 0.7
>            Reporter: Stu Hood
>            Priority: Blocker
>             Fix For: 0.5, 0.6, 0.7
>
>         Attachments: short-term-790-check-for-overflow-and-cap-bloom-size.txt
>
>
> The current BloomFilter implementation requires a BitSet of (bucket_count * num_keys)
in size, and that calculation is currently performed in an integer, which causes overflow
for around 140 million keys in one SSTable.
> Short term fix: perform the calculation in a long, and cap the value to the maximum size
of a BitSet.
> Long term fix: begin partitioning BitSets, perhaps using Linear Bloom Filters.

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