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From "stack (JIRA)" <j...@apache.org>
Subject [jira] Created: (HBASE-2531) 32-bit encoding of regionnames waaaaaaayyyyy too susceptible to hash clashes
Date Tue, 11 May 2010 05:31:29 GMT
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: 0.20.5, 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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