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From "Tsz Wo (Nicholas), SZE (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HDFS-5285) Flatten INodeFile hierarchy
Date Tue, 01 Oct 2013 14:58:28 GMT
Tsz Wo (Nicholas), SZE created HDFS-5285:

             Summary: Flatten INodeFile hierarchy
                 Key: HDFS-5285
                 URL: https://issues.apache.org/jira/browse/HDFS-5285
             Project: Hadoop HDFS
          Issue Type: Sub-task
          Components: namenode
            Reporter: Tsz Wo (Nicholas), SZE
            Assignee: Tsz Wo (Nicholas), SZE

For files, there are INodeFile, INodeFileUnderConstruction, INodeFileWithSnapshot and INodeFileUnderConstructionWithSnapshot
for representing whether a file is under construction or whether it is in some snapshot. 
The following are two major problems of the current approach:
- Java class does not support multiple inheritances so that INodeFileUnderConstructionWithSnapshot
cannot extend both INodeFileUnderConstruction and INodeFileWithSnapshot.
- The number of classes is exponential to the number of features.  Currently, there are only
two features, UnderConstruction and WithSnapshot.  The number of classes is 2^2 = 4.  It is
hard to add one more feature since the number of classes will become 2^3 = 8.

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