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From "Jonathan Ellis (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-4303) Compressed bloomfilters
Date Fri, 01 Jun 2012 02:53:22 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-4303?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13287109#comment-13287109
] 

Jonathan Ellis commented on CASSANDRA-4303:
-------------------------------------------

This was the nail in the EWAH coffin:

bq. EWAH looks like it might be useful for reducing on-disk storage for BFs, but it doesn't
appear to be useful for in-memory usage because the cost of checking a bit is linear, not
constant. 
                
> Compressed bloomfilters
> -----------------------
>
>                 Key: CASSANDRA-4303
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-4303
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: Brandon Williams
>             Fix For: 1.2
>
>
> Very commonly, people encountering an OOM need to increase their bloom filter false positive
ratio to reduce memory pressure, since BFs tend to be the largest shareholder.  It would make
sense if we could alleviate the memory pressure from BFs with compression while maintaining
the FP ratio (at the cost of a bit of cpu) that some users have come to expect.  One possible
implementation is at http://code.google.com/p/javaewah/

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