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From "Jim Kellerman (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HBASE-696) Make bloomfilter true/false and self-sizing
Date Tue, 08 Jul 2008 23:36:31 GMT

    [ https://issues.apache.org/jira/browse/HBASE-696?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12611846#action_12611846
] 

Jim Kellerman commented on HBASE-696:
-------------------------------------

> -----Original Message-----
> From: Jim Kellerman 
> Sent: Tuesday, July 08, 2008 4:31 PM
> To: hbase-user
> Subject: RE: HBASE-696 Make bloomfilter true/false and self-sizing
> 
> Unless there is significant feedback to the contrary, making 
> bloom filters true/false and self sizing will be an 
> incompatible change.
> 
> During migration, columns which have bloom filters enabled 
> currently will have the bloom filter erased and disabled.
> 
> Columns may bloom filters only if they are enabled when the 
> column is created.
> 
> If a column is later modified to disable the bloom filter, it 
> will be erased and cannot be re-enabled.
> 
> There is one short term (0.2.0) option for migration and 
> enabling bloom filters which will be very expensive: reading 
> the column twice, first to establish the number of entries 
> that are needed and second, to create the bloom filter.
> 
> There is one long term option: convince Hadoop that MapFile 
> should be subclassable which would entail changing private 
> members to protected members, or to provide accessors to the 
> private members in MapFile. Because hadoop-0.18.0 is in 
> feature freeze, any change of this sort would have to wait 
> for hadoop-0.19.0. hbase-0.3.0 will target hadoop-0.18.x, so 
> this change would have to wait until hbase-0.4.0.
> 
> The question is how many people use bloom filters today? It 
> is our belief that they are not particularly useful as 
> implemented. If you do use bloom filters today, would you 
> object to a process by which you would create a new bloom 
> filter enabled column and copy your data to the new column?
> 
> ---
> Jim Kellerman, Senior Engineer; Powerset


> Make bloomfilter true/false and self-sizing
> -------------------------------------------
>
>                 Key: HBASE-696
>                 URL: https://issues.apache.org/jira/browse/HBASE-696
>             Project: Hadoop HBase
>          Issue Type: Improvement
>            Reporter: stack
>            Assignee: Jim Kellerman
>             Fix For: 0.2.0
>
>
> Remove bloomfilter options.  Only one bloomfilter type makes sense in hbase context.
 Also, make bloomfilter self-sizing; you know size when flushing.
> Putting in 0.2 for now because its API change (for the simpler).  We can punt later.

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