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Date: Fri, 23 Dec 2011 04:03:30 +0000 (UTC)
From: "Jonathan Ellis (Updated) (JIRA)" <jira@apache.org>
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Subject: [jira] [Updated] (CASSANDRA-3497) BloomFilter FP ratio should be
 configurable or size-restricted some other way
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     [ https://issues.apache.org/jira/browse/CASSANDRA-3497?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Jonathan Ellis updated CASSANDRA-3497:
--------------------------------------

    Attachment: 3497-v3.txt

Sorry, I didn't look closely enough the first time.  The BloomFilter#modify approach won't work: when we change the BF parameters we change what bits should be set -- there's no way to rebuild it with new parameters without re-inserting all the keys.

Attached v3 that just changes the BloomFilter constructor in SSTableWriter.  (So, people will have to scrub to rebuild things, but that's the best we can do.)  Also changed the setting to bloom_filter_fp_chance and updated cli help.

How does that look to you?
                
> BloomFilter FP ratio should be configurable or size-restricted some other way
> -----------------------------------------------------------------------------
>
>                 Key: CASSANDRA-3497
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-3497
>             Project: Cassandra
>          Issue Type: New Feature
>          Components: Core
>            Reporter: Brandon Williams
>            Assignee: Yuki Morishita
>            Priority: Minor
>             Fix For: 1.0.7
>
>         Attachments: 3497-v3.txt, CASSANDRA-1.0-3497.txt
>
>
> When you have a live dc and purely analytical dc, in many situations you can have less nodes on the analytical side, but end up getting restricted by having the BloomFilters in-memory, even though you have absolutely no use for them.  It would be nice if you could reduce this memory requirement by tuning the desired FP ratio, or even just disabling them altogether.

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