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https://issues.apache.org/jira/browse/SPARK-10429?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14742251#comment-14742251
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Yin Huai commented on SPARK-10429:
----------------------------------
[Here |
https://github.com/apache/spark/blob/master/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/codegen/GenerateMutableProjection.scala#L41-L66]
is the code block that needs to be changed.
> 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
> 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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