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https://issues.apache.org/jira/browse/SPARK-13333?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15939347#comment-15939347
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Xiao Li commented on SPARK-13333:
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[~josephkb] In the SQL specification, the set operations are merging columns by 
column positions. However, it also provides another keyword {{CORRESPONDING}}. 
If users specify that keyword with set operations, we will merge them by column 
names, regardless of their positions. Do you want this feature? I can do it in 
the next release, since Spark 2.2 will be released soon. 

> DataFrame filter + randn + unionAll has bad interaction
> -------------------------------------------------------
>
>                 Key: SPARK-13333
>                 URL: https://issues.apache.org/jira/browse/SPARK-13333
>             Project: Spark
>          Issue Type: Bug
>          Components: SQL
>    Affects Versions: 1.4.2, 1.6.1, 2.0.0
>            Reporter: Joseph K. Bradley
>
> Buggy workflow
> * Create a DataFrame df0
> * Filter df0
> * Add a randn column
> * Create a copy of the DataFrame
> * unionAll the two DataFrames
> This fails, where randn produces the same results on the original DataFrame 
> and the copy before unionAll but fails to do so after unionAll.  Removing the 
> filter fixes the problem.
> The bug can be reproduced on master:
> {code}
> import org.apache.spark.sql.functions.randn
> val df0 = sqlContext.createDataFrame(Seq(0, 1).map(Tuple1(_))).toDF("id")
> // Removing the following filter() call makes this give the expected result.
> val df1 = df0.filter(col("id") === 0).withColumn("b", randn(12345))
> println("DF1")
> df1.show()
> val df2 = df1.select("id", "b")
> println("DF2")
> df2.show()  // same as df1.show(), as expected
> val df3 = df1.unionAll(df2)
> println("DF3")
> df3.show()  // NOT two copies of df1, which is unexpected
> {code}



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