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https://issues.apache.org/jira/browse/HDFS-512?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12738568#action_12738568
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Konstantin Shvachko commented on HDFS-512:
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I was looking at compareTo(), which is used in TreeMap. HashMap uses equals()
so yes all maps are affected.
I still think the change makes sense because we don't want to treat the same
block with different generation stamps as separate blocks.
By the way, equals() should probably be implemented via compareTo() so that
they are always in sync.
> Set block id as the key to Block
> --------------------------------
>
> Key: HDFS-512
> URL: https://issues.apache.org/jira/browse/HDFS-512
> Project: Hadoop HDFS
> Issue Type: Improvement
> Affects Versions: 0.21.0
> Reporter: Hairong Kuang
> Assignee: Hairong Kuang
> Fix For: 0.21.0
>
> Attachments: blockKey.patch
>
>
> Currently the key to Block is block id + generation stamp. I would propose to
> change it to be only block id. This is based on the following properties of
> the dfs cluster:
> 1. On each datanode only one replica of block exists. Therefore there is only
> one generation of a block.
> 2. NameNode has only one entry for a block in its blocks map.
> With this change, search for a block/replica's meta information is easier
> since most of the time we know a block's id but may not know its generation
> stamp.
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