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https://issues.apache.org/jira/browse/HDFS-7174?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14156643#comment-14156643
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Kihwal Lee commented on HDFS-7174:
----------------------------------
I manually run the test-patch and verified that no new javac warnings are
generated with the patch. I checked the diff of warnings. In fact, the build
log says this:
{panel}
There appear to be 1264 javac compiler warnings before the patch and 1264 javac
compiler warnings after applying the patch
{panel}
I am not sure why it decided to say there are two new warnings.
The failures in TestCommitBlockSynchronization is caused by the patch. Without
the patch, searching for an inode with {{null}} name in a directory always
returns a valid index, 0, even if there is no such entry. So, if the name of an
inode is {{null}}, any {{INodeDirectory}} instances will think it has this
inode as a child! The test case was relying on this broken behavior. It
doesn't even actually need to call {{parent.addChild(file)}}.
I will fix the test case.
> Support for more efficient large directories
> --------------------------------------------
>
> Key: HDFS-7174
> URL: https://issues.apache.org/jira/browse/HDFS-7174
> Project: Hadoop HDFS
> Issue Type: Improvement
> Reporter: Kihwal Lee
> Assignee: Kihwal Lee
> Priority: Critical
> Attachments: HDFS-7174.patch, HDFS-7174.patch
>
>
> When the number of children under a directory grows very large, insertion
> becomes very costly. E.g. creating 1M entries takes 10s of minutes. This is
> because the complexity of an insertion is O\(n\). As the size of a list
> grows, the overhead grows n^2. (integral of linear function). It also causes
> allocations and copies of big arrays.
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