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https://issues.apache.org/jira/browse/SPARK-19665?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Liang-Chi Hsieh closed SPARK-19665.
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Resolution: Won't Fix
> Improve constraint propagation
> ------------------------------
>
> Key: SPARK-19665
> URL: https://issues.apache.org/jira/browse/SPARK-19665
> Project: Spark
> Issue Type: Improvement
> Components: SQL
> Affects Versions: 2.1.0
> Reporter: Liang-Chi Hsieh
>
> If there are aliased expression in the projection, we propagate constraints
> by completely expanding the original constraints with aliases.
> This expanding costs much computation time when the number of aliases
> increases.
> Another issue is we actually don't need the additional constraints at most of
> time. For example, if there is a constraint "a > b", and "a" is aliased to
> "c" and "d". When we use this constraint in filtering, we don't need all
> constraints "a > b", "c > b", "d > b". We only need "a > b" because if it is
> false, it is guaranteed that all other constraints are false too.
> Fully expanding all constraints at all the time makes iterative ML algorithms
> where a ML pipeline with many stages runs very slow.
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