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https://issues.apache.org/jira/browse/HDFS-8499?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14635605#comment-14635605
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Tsz Wo Nicholas Sze commented on HDFS-8499:
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> .. Along the history, an invariant is that an under-construction block is-a
> type of block. This is the is-a relationship that I think design #2 breaks.
As mentioned previously, "The only drawback is that a BlockInfoUC is not a
BlockInfo. It is fine since BlockInfoUC is only an interface – the
implementation classes always is-a BlockInfo by the disgram below. We always
can safely cast a BlockInfoUC object to BlockInfo." Design #2 does not really
break "an under-construction block is-a type of block".
> Refactor BlockInfo class hierarchy with static helper class
> -----------------------------------------------------------
>
> Key: HDFS-8499
> URL: https://issues.apache.org/jira/browse/HDFS-8499
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: namenode
> Affects Versions: 2.7.0
> Reporter: Zhe Zhang
> Assignee: Zhe Zhang
> Fix For: 2.8.0
>
> Attachments: HDFS-8499.00.patch, HDFS-8499.01.patch,
> HDFS-8499.02.patch, HDFS-8499.03.patch, HDFS-8499.04.patch,
> HDFS-8499.05.patch, HDFS-8499.06.patch, HDFS-8499.07.patch,
> HDFS-8499.UCFeature.patch, HDFS-bistriped.patch
>
>
> In HDFS-7285 branch, the {{BlockInfoUnderConstruction}} interface provides a
> common abstraction for striped and contiguous UC blocks. This JIRA aims to
> merge it to trunk.
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