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From "Jonathan Ellis (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-6633) Dynamic Resize of Bloom Filters
Date Wed, 04 Feb 2015 03:36:35 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-6633?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14304598#comment-14304598
] 

Jonathan Ellis commented on CASSANDRA-6633:
-------------------------------------------

bq. separate address spaces for each hash function

I'm not sure what you mean here.  Bloom filters save space by combining hashes in a single
bucket space, so I don't see how you can add separate spaces to that and still have a BF.

> Dynamic Resize of Bloom Filters
> -------------------------------
>
>                 Key: CASSANDRA-6633
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-6633
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>            Reporter: Benedict
>            Priority: Minor
>              Labels: performance
>             Fix For: 3.0
>
>
> Dynamic resizing would be useful. The simplest way to achieve this is to have separate
address spaces for each hash function, so that we may increase/decrease accuracy by simply
loading/unloading another function (we could even do interesting stuff in future like alternating
the functions we select if we find we're getting more false positives than should be expected);
> Faster loading/unloading would help this, and we could achieve this by mmapping the bloom
filter representation on systems that we can mlock.



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