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Posted to issues@hbase.apache.org by "stack (JIRA)" <ji...@apache.org> on 2010/05/11 07:49:30 UTC
[jira] Commented: (HBASE-2531) 32-bit encoding of regionnames
waaaaaaayyyyy too susceptible to hash clashes
[ https://issues.apache.org/jira/browse/HBASE-2531?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12866066#action_12866066 ]
stack commented on HBASE-2531:
------------------------------
After some discussion up on IRC -- todd, posix4e, jdcryans, kannan -- and thought was that UUID would make the most sense.
> 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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