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https://issues.apache.org/jira/browse/SPARK-18505?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Reynold Xin resolved SPARK-18505.
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Resolution: Fixed
Fix Version/s: 2.1.0
> Simplify AnalyzeColumnCommand
> -----------------------------
>
> Key: SPARK-18505
> URL: https://issues.apache.org/jira/browse/SPARK-18505
> Project: Spark
> Issue Type: Sub-task
> Components: SQL
> Reporter: Reynold Xin
> Assignee: Reynold Xin
> Fix For: 2.1.0
>
>
> I'm spending more time at the design & code level for cost-based optimizer
> now, and have found a number of issues related to maintainability and
> compatibility that I will like to address.
> This is a small pull request to clean up AnalyzeColumnCommand:
> 1. Removed warning on duplicated columns. Warnings in log messages are
> useless since most users that run SQL don't see them.
> 2. Removed the nested updateStats function, by just inlining the function.
> 3. Renamed a few functions to better reflect what they do.
> 4. Removed the factory apply method for ColumnStatStruct. It is a bad pattern
> to use a apply method that returns an instantiation of a class that is not of
> the same type (ColumnStatStruct.apply used to return CreateNamedStruct).
> 5. Renamed ColumnStatStruct to just AnalyzeColumnCommand.
> 6. Added more documentation explaining some of the non-obvious return types
> and code blocks.
> In follow-up pull requests, I'd like to address the following:
> 1. Get rid of the Map[String, ColumnStat] map, since internally we should be
> using Attribute to reference columns, rather than strings.
> 2. Decouple the fields exposed by ColumnStat and internals of Spark SQL's
> execution path. Currently the two are coupled because ColumnStat takes in an
> InternalRow.
> 3. Correctness: Remove code path that stores statistics in the catalog using
> the base64 encoding of the UnsafeRow format, which is not stable across Spark
> versions.
> 4. Clearly document the data representation stored in the catalog for
> statistics.
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