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From "Mingliang Liu (JIRA)" <j...@apache.org>
Subject [jira] [Comment Edited] (HADOOP-13368) DFSOpsCountStatistics$OpType#fromSymbol and s3a.Statistic#fromSymbol should be O(1) operation
Date Wed, 13 Jul 2016 18:14:20 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-13368?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15375477#comment-15375477
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Mingliang Liu edited comment on HADOOP-13368 at 7/13/16 6:13 PM:
-----------------------------------------------------------------

Per offline discussion with [~Hitesh], the v1 patch sets the initial capacity of the hashmap
to account for the load factor as we know the size of the enum.


was (Author: liuml07):
Per offline discussion with [~Hitesh], the v1 patch setsthe initial capacity of the hashmap
to account for the load factor as we know the size of the enum.

> DFSOpsCountStatistics$OpType#fromSymbol and s3a.Statistic#fromSymbol should be O(1) operation
> ---------------------------------------------------------------------------------------------
>
>                 Key: HADOOP-13368
>                 URL: https://issues.apache.org/jira/browse/HADOOP-13368
>             Project: Hadoop Common
>          Issue Type: Sub-task
>          Components: fs
>    Affects Versions: 2.8.0
>            Reporter: Mingliang Liu
>            Assignee: Mingliang Liu
>             Fix For: 2.8.0
>
>         Attachments: HADOOP-13368.000.patch, HADOOP-13368.001.patch
>
>
> To lookup, {{DFSOpsCountStatistics$OpType#fromSymbol}} and {{s3a.Statistic#fromSymbol}}
iterates all the enums to get the entry by its symbol. Usages of {{fromSymbol()}} include
{{isTracked()}} and {{getLong()}}. 
> As there are dozens of enum entries, it merits to make these two similar operations O(1)
complexity. This point is especially true if downstream app probes a dozen of stats in an
outer loop (see [TEZ-3331]).



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