[jira] [Commented] (SPARK-19536) Improve capability to merge SQL data types

["Hyukjin Kwon (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/SPARK-19536?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15860665#comment-15860665 ] 

Hyukjin Kwon commented on SPARK-19536:
--------------------------------------

Oh, for {{ArrayType}}, I filed a JIRA, SPARK-19435 and opened a PR, https://github.com/apache/spark/pull/16777

> Improve capability to merge SQL data types
> ------------------------------------------
>
>                 Key: SPARK-19536
>                 URL: https://issues.apache.org/jira/browse/SPARK-19536
>             Project: Spark
>          Issue Type: Improvement
>          Components: SQL
>    Affects Versions: 2.1.0
>            Reporter: koert kuipers
>            Priority: Minor
>
> spark's union/merging of compatible types seems kind of weak. it works on basic types in the top level record, but it fails for nested records, maps, arrays, etc.
> i would like to improve this.
> for example i get errors like this:
> {noformat}
> org.apache.spark.sql.AnalysisException: Union can only be performed on tables with the compatible column types. StructType(StructField(_1,StringType,true), StructField(_2,IntegerType,false)) <> StructType(StructField(_1,StringType,true), StructField(_2,LongType,false)) at the first column of the second table
> {noformat}
> some examples that do work:
> {noformat}
> scala> Seq(1, 2, 3).toDF union Seq(1L, 2L, 3L).toDF
> res2: org.apache.spark.sql.Dataset[org.apache.spark.sql.Row] = [value: bigint]
> scala> Seq((1,"x"), (2,"x"), (3,"x")).toDF union Seq((1L,"x"), (2L,"x"), (3L,"x")).toDF
> res3: org.apache.spark.sql.Dataset[org.apache.spark.sql.Row] = [_1: bigint, _2: string]
> {noformat}
> what i would also expect to work but currently doesn't:
> {noformat}
> scala> Seq((Seq(1),"x"), (Seq(2),"x"), (Seq(3),"x")).toDF union Seq((Seq(1L),"x"), (Seq(2L),"x"), (Seq(3L),"x")).toDF
> scala> Seq((1,("x",1)), (2,("x",2)), (3,("x",3))).toDF union Seq((1L,("x",1L)), (2L,("x",2L)), (3L,("x", 3L))).toDF
> {noformat}



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