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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (KYLIN-3398) Inaccurate arithmetic operation in LookupTableToHFileJob#calculateShardNum
Date Sun, 10 Jun 2018 06:32:00 GMT

    [ https://issues.apache.org/jira/browse/KYLIN-3398?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16507272#comment-16507272
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ASF GitHub Bot commented on KYLIN-3398:
---------------------------------------

asfgit commented on issue #152: KYLIN-3398 Fix inaccurate arithmetic operations
URL: https://github.com/apache/kylin/pull/152#issuecomment-396024485
 
 
   Can one of the admins verify this patch?

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> Inaccurate arithmetic operation in LookupTableToHFileJob#calculateShardNum
> --------------------------------------------------------------------------
>
>                 Key: KYLIN-3398
>                 URL: https://issues.apache.org/jira/browse/KYLIN-3398
>             Project: Kylin
>          Issue Type: Bug
>            Reporter: Ted Yu
>            Assignee: jiatao.tao
>            Priority: Major
>
> There're two issues with the following code:
> {code}
>     private int calculateShardNum(KylinConfig kylinConfig, long dataSize) {
>         long shardSize = kylinConfig.getExtTableSnapshotShardingMB() * 1024 * 1024;
>         return dataSize < shardSize ? 1 : (int) (Math.ceil(dataSize / shardSize));
> {code}
> getExtTableSnapshotShardingMB returns an int. The multiplication is done using 32-bit
arithmetic, and then used in a context that expects an expression of type "long".
> Second, Math.ceil expects a double. The integer division would lose some precision.



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