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https://issues.apache.org/jira/browse/SPARK-10429?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14986238#comment-14986238
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Apache Spark commented on SPARK-10429:
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User 'davies' has created a pull request for this issue:
https://github.com/apache/spark/pull/9422
> MutableProjection should evaluate all expressions first and then update the
> mutable row
> ---------------------------------------------------------------------------------------
>
> Key: SPARK-10429
> URL: https://issues.apache.org/jira/browse/SPARK-10429
> Project: Spark
> Issue Type: Sub-task
> Components: SQL
> Reporter: Yin Huai
> Assignee: Davies Liu
> Priority: Blocker
>
> Right now, SQL's mutable projection updates every value of the mutable
> project after it evaluates the corresponding expression. This makes the
> behavior of MutableProjection confusing and complicate the implementation of
> common aggregate functions like stddev because developers need to be aware
> that when evaluating {{i+1}}th expression of a mutable projection, {{i}}th
> slot of the mutable row has already been updated.
> A better behavior of MutableProjection will be that we evaluate all
> expressions first and then update all values of the mutable row.
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