[GitHub] spark pull request: [Minor][SQL] Little refactor DataFrame related...

[rxin <gi...@git.apache.org>]

Github user rxin commented on a diff in the pull request:

    https://github.com/apache/spark/pull/4298#discussion_r23895621
  
    --- Diff: sql/core/src/main/scala/org/apache/spark/sql/DataFrame.scala ---
    @@ -139,12 +139,13 @@ class DataFrame protected[sql](
        *   val rdd: RDD[(Int, String)] = ...
        *   rdd.toDataFrame  // this implicit conversion creates a DataFrame with column name _1 and _2
        *   rdd.toDataFrame("id", "name")  // this creates a DataFrame with column name "id" and "name"
    +   *   rdd.toDataFrame("id")          // this creates a DataFrame with only column name "id"
        * }}}
        */
       @scala.annotation.varargs
       def toDataFrame(colName: String, colNames: String*): DataFrame = {
         val newNames = colName +: colNames
    -    require(schema.size == newNames.size,
    +    require(schema.size >= newNames.size,
    --- End diff --
    
    I'm worried that silently dropping fields here can cause trouble without the user knowing. Can you revert this line?
    
    If we see a lot of requests to make it less strict, we can always relax it in the future. But we cannot go the other way.


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