[GitHub] spark pull request #18228: [SPARK-21007][SQL]Add SQL function - RIGHT && LEF...

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

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

    https://github.com/apache/spark/pull/18228#discussion_r126266425
  
    --- Diff: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/stringExpressions.scala ---
    @@ -1199,6 +1199,85 @@ case class Substring(str: Expression, pos: Expression, len: Expression)
     }
     
     /**
    + * Returns the rightmost n characters from the string.
    + */
    +@ExpressionDescription(
    +  usage = "_FUNC_(str, len) - Returns the rightmost `len` characters from the string `str`.",
    +  extended = """
    +    Examples:
    +      > SELECT _FUNC_('Spark SQL', 3);
    +       SQL
    +  """)
    +case class Right(str: Expression, len: Expression)
    +  extends BinaryExpression with ImplicitCastInputTypes with NullIntolerant {
    +  override def left: Expression = str
    +  override def right: Expression = len
    +  override def dataType: DataType = str.dataType
    +
    +  override def inputTypes: Seq[AbstractDataType] =
    +    Seq(TypeCollection(StringType, BinaryType), IntegerType)
    +
    +  override def nullSafeEval(string: Any, len: Any): Any = {
    +    str.dataType match {
    +      case StringType => string.asInstanceOf[UTF8String]
    +        .substringSQL(if (len.asInstanceOf[Int] <= 0) Integer.MAX_VALUE else -len.asInstanceOf[Int],
    +          Integer.MAX_VALUE)
    --- End diff --
    
    Please change it to something like
    ```
    val pos = xyz
    val len = xyz
    string.asInstanceOf[UTF8String].substringSQL(pos, len)
    ```


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