[GitHub] spark pull request #16476: [SPARK-19084][SQL][WIP] Implement expression fiel...

[chenghao-intel <gi...@git.apache.org>]

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

    https://github.com/apache/spark/pull/16476#discussion_r95281046
  
    --- Diff: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/conditionalExpressions.scala ---
    @@ -340,3 +344,102 @@ object CaseKeyWhen {
         CaseWhen(cases, elseValue)
       }
     }
    +
    +/**
    + * A function that returns the index of expr in (expr1, expr2, ...) list or 0 if not found.
    + * It takes at least 2 parameters, and all parameters should be subtype of AtomicType or NullType.
    + * It's also acceptable to give parameters of different types.
    + * If the search string is NULL, the return value is 0 because NULL fails equality comparison with any value.
    + * When the paramters have different types, comparing will be done based on type firstly,
    + * for example, ''999'' won't be considered equal with 999, no implicit cast will be done here.
    + */
    +@ExpressionDescription(
    +  usage = "_FUNC_(expr, expr1, expr2, ...) - Returns the index of expr in the expr1, expr2, ... or 0 if not found.",
    +  extended = """
    +    Examples:
    +      > SELECT _FUNC_(10, 9, 3, 10, 4);
    +       3
    +      > SELECT _FUNC_('a', 'b', 'c', 'd', 'a');
    +       4
    +      > SELECT _FUNC_('999', 'a', 999, 9.99, '999');
    +       4
    +  """)
    +case class Field(children: Seq[Expression]) extends Expression {
    +
    +  /** Even if expr is not found in (expr1, expr2, ...) list, the value will be 0, not null */
    +  override def nullable: Boolean = false
    +  override def foldable: Boolean = children.forall(_.foldable)
    +
    +  private lazy val ordering = TypeUtils.getInterpretedOrdering(children(0).dataType)
    +
    +  private val dataTypeMatchIndex: Seq[Int] = children.tail.zip(Stream from 1).filter(
    --- End diff --
    
    Array[Int] instead? Seq[Int] probably a LinkedList in its concrete implementation.


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