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From "dhruba borthakur (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HBASE-2531) 32-bit encoding of regionnames waaaaaaayyyyy too susceptible to hash clashes
Date Tue, 18 May 2010 05:58:43 GMT

    [ https://issues.apache.org/jira/browse/HBASE-2531?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12868543#action_12868543
] 

dhruba borthakur commented on HBASE-2531:
-----------------------------------------

> Going forward it will not be needed since the UUID will actually be part of the region
name.

@Stack, thanks for the info.  If the UUD is part of the regionname, then does this mean that
nothing needs to be done for this JIRA? If that is not the case and we want to do somethinkg
for this JIRS, can you pl explain what needs to be done? Thanks.

> 32-bit encoding of regionnames waaaaaaayyyyy too susceptible to hash clashes
> ----------------------------------------------------------------------------
>
>                 Key: HBASE-2531
>                 URL: https://issues.apache.org/jira/browse/HBASE-2531
>             Project: Hadoop HBase
>          Issue Type: Bug
>            Reporter: stack
>            Assignee: stack
>            Priority: Blocker
>             Fix For: 0.21.0
>
>
> Kannan tripped over two regionnames that hashed the same:
> Here is code demo'ing that his two names hash the same:
> {code}
> package org;
> import org.apache.hadoop.hbase.util.Bytes;
> import org.apache.hadoop.hbase.util.JenkinsHash;
> public class Testing {
>   public static void main(final String [] args) {
>     System.out.println(encodeRegionName(Bytes.toBytes("test1,6838000000,1273541236167")));
>     System.out.println(encodeRegionName(Bytes.toBytes("test1,0520100000,1273541610201")));
>   }
>   /**
>    * @param regionName
>    * @return the encodedName
>    */
>   public static int encodeRegionName(final byte [] regionName) {
>     return Math.abs(JenkinsHash.getInstance().hash(regionName, regionName.length, 0));
>   }
> }
> {code}
> Need new encoding mechanism.  Will need to migrate old regions to new schema.

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