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From marmbrus <...@git.apache.org>
Subject [GitHub] spark pull request: [SPARK-2053][SQL] Add Catalyst expressions for...
Date Thu, 12 Jun 2014 01:05:47 GMT
Github user marmbrus commented on a diff in the pull request:

    https://github.com/apache/spark/pull/1055#discussion_r13683452
  
    --- Diff: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/predicates.scala
---
    @@ -202,3 +203,139 @@ case class If(predicate: Expression, trueValue: Expression, falseValue:
Expressi
     
       override def toString = s"if ($predicate) $trueValue else $falseValue"
     }
    +
    +// scalastyle:off
    +/**
    + * Case statements of the form "CASE WHEN a THEN b [WHEN c THEN d]* [ELSE e] END".
    + * Refer to this link for the corresponding semantics:
    + * https://cwiki.apache.org/confluence/display/Hive/LanguageManual+UDF#LanguageManualUDF-ConditionalFunctions
    + *
    + * Note that branches are considered in consecutive pairs (cond, val), and the optional
last element
    + * is the val for the default catch-all case (if provided). Hence, `branches` consist
of at least
    + * two elements, and can have an odd or even length.
    + */
    +// scalastyle:on
    +case class CaseWhen(branches: Seq[Expression]) extends Expression {
    +  type EvaluatedType = Any
    +  def children = branches
    +  def references = children.flatMap(_.references).toSet
    +  def dataType = {
    +    if (!resolved) {
    +      throw new UnresolvedException(this, "cannot resolve due to differing types in some
branches")
    +    }
    +    branches(1).dataType
    +  }
    +
    +  override def nullable = branches.sliding(2, 2).map {
    +      case Seq(cond, value) => value.nullable
    +      case Seq(elseValue) => elseValue.nullable
    +    }.reduce(_ || _)
    +
    +  override lazy val resolved = {
    +    lazy val allCondBooleans = branches.sliding(2, 2).map {
    --- End diff --
    
    Is there a reason to make these inner variables lazy?


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