[GitHub] spark pull request #16476: [SPARK-19084][SQL] Implement expression field

[gczsjdy]

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

    https://github.com/apache/spark/pull/16476#discussion_r95080295
  
    --- Diff: 
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/conditionalExpressions.scala
 ---
    @@ -340,3 +341,91 @@ object CaseKeyWhen {
         CaseWhen(cases, elseValue)
       }
     }
    +
    +/**
    + * A function that returns the index of str in (str1, str2, ...) list or 0 
if not found.
    + * It takes at least 2 parameters, and all parameters' types should be 
subtypes of AtomicType.
    + */
    +@ExpressionDescription(
    +  usage = "_FUNC_(str, str1, str2, ...) - Returns the index of str in the 
str1,str2,... or 0 if not found.",
    +  extended = """
    +    Examples:
    +      > SELECT _FUNC_(10, 9, 3, 10, 4);
    +       3
    +  """)
    +case class Field(children: Seq[Expression]) extends Expression {
    +
    +  override def nullable: Boolean = false
    +  override def foldable: Boolean = children.forall(_.foldable)
    +
    +  private lazy val ordering = 
TypeUtils.getInterpretedOrdering(children(0).dataType)
    +
    +  override def checkInputDataTypes(): TypeCheckResult = {
    +    if (children.length <= 1) {
    +      TypeCheckResult.TypeCheckFailure(s"FIELD requires at least 2 
arguments")
    +    } else if (!children.forall(_.dataType.isInstanceOf[AtomicType])) {
    +      TypeCheckResult.TypeCheckFailure(s"FIELD requires all arguments to 
be of AtomicType")
    +    } else
    +      TypeCheckResult.TypeCheckSuccess
    +  }
    +
    +  override def dataType: DataType = IntegerType
    +
    +  override def eval(input: InternalRow): Any = {
    +    val target = children.head.eval(input)
    +    val targetDataType = children.head.dataType
    +    def findEqual(target: Any, params: Seq[Expression], index: Int): Int = 
{
    +      params.toList match {
    --- End diff --
    
    @gatorsmile Actually, the case:
    `checkAnswer(testData.selectExpr("field('花花世界', 'a', 1.23, true, 
'花花世界')"), Row(4))`
    will produce a child: Seq[Expression] an ArrayBuffer, it's not a list, so 
can't use head::tail.
    So there are 2 ways: 
    1. remove the `toList` and do another pattern match for ArrayBuffer, which 
I think is not neat.
    2. keep the `toList`.



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