[GitHub] [spark] hemanthmeka commented on issue #25570: [SPARK-23519][SQL] create view should work from query with duplicate output columns

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hemanthmeka commented on issue #25570: [SPARK-23519][SQL] create view should work from query with duplicate output columns
URL: https://github.com/apache/spark/pull/25570#issuecomment-524820928
 
 
   > > ALTER VIEW AS gets its schema from the new SELECT query provided. So it is not effected
   > 
   > But `sql("ALTER VIEW v23519 AS SELECT c1, c1 FROM t23519")` also fails with an exception?
   > 
   > ```scala
   > org.apache.spark.sql.AnalysisException: Found duplicate column(s) in the view definition: `c1`;
   > [info]   at org.apache.spark.sql.util.SchemaUtils$.checkColumnNameDuplication(SchemaUtils.scala:90)                                                   
   > [info]   at org.apache.spark.sql.util.SchemaUtils$.checkColumnNameDuplication(SchemaUtils.scala:70)                                                   
   > [info]   at org.apache.spark.sql.execution.command.ViewHelper$.generateViewProperties(views.scala:369)
   > [info]   at org.apache.spark.sql.execution.command.AlterViewAsCommand.alterPermanentView(views.scala:301)
   > ```
   
   From the comments in CreateViewCommand.run('**Nothing we need to retain from the old view, so ...**') i get the impression that alter always creates a new definition with schema from query, then c1, c1 should throw analysis exception. Which should be the right behaviour? Any reference?
   
   

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