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Posted to hdfs-issues@hadoop.apache.org by "Allen Wittenauer (JIRA)" <ji...@apache.org> on 2015/05/06 05:37:41 UTC

[jira] [Updated] (HDFS-7174) Support for more efficient large directories

     [ https://issues.apache.org/jira/browse/HDFS-7174?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Allen Wittenauer updated HDFS-7174:
-----------------------------------
    Labels: BB2015-05-TBR  (was: )

> 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
>              Labels: BB2015-05-TBR
>         Attachments: HDFS-7174.new.patch, 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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