Github user chenghao-intel commented on a diff in the pull request:

    https://github.com/apache/spark/pull/8026#discussion_r42506907
  
    --- Diff: 
sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/PartitioningUtils.scala
 ---
    @@ -236,15 +241,22 @@ private[sql] object PartitioningUtils {
       }
     
       /**
    -   * Converts a string to a [[Literal]] with automatic type inference.  
Currently only supports
    -   * [[IntegerType]], [[LongType]], [[DoubleType]], 
[[DecimalType.SYSTEM_DEFAULT]], and
    -   * [[StringType]].
    +   * Converts a string to a [[Literal]] with automatic type inference if 
no field type specified.
    +   * Auto inference only supports [[IntegerType]], [[LongType]], 
[[DoubleType]],
    +   * [[DecimalType.SYSTEM_DEFAULT]], and [[StringType]].
        */
       private[sql] def inferPartitionColumnValue(
    +      expectedDT: Option[DataType],
    --- End diff --
    
    We need to pass the expect the data type down and then get the associated 
literal-based partition column value; and @liancheng's suggestion kind of like 
get the literal (maybe string based) first, and then do casting outside, 
however, this probably lose some data precision during the re-casting.
    
    For example:
    The path looks like, /part1=1.000, and with the auto inference, we will get 
a Double, and it will be cast to string as `1.0` if what user expect is 
StringType;
    
    However, this is totally different if we get it as StringType directly, 
which supposed to be `1.000`.


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