Github user ggupta81 commented on a diff in the pull request:
https://github.com/apache/spark/pull/8113#discussion_r36826491
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/aggregates.scala
---
@@ -630,59 +632,114 @@ case class CombineSetsAndSumFunction(
}
}
-case class First(child: Expression) extends UnaryExpression with
PartialAggregate1 {
+case class First(
+ child: Expression,
+ ignoreNulls: Boolean)
+ extends UnaryExpression with PartialAggregate1 {
+
+ def this(child: Expression) = this(child, false)
+
+ def this(child: Expression, ignoreNulls: Expression) = this(child,
ignoreNulls match {
+ case Literal(b: Boolean, BooleanType) => b
+ case _ =>
+ throw new AnalysisException("The second argument of First should be
a boolean literal.")
+ })
+
override def nullable: Boolean = true
override def dataType: DataType = child.dataType
- override def toString: String = s"FIRST($child)"
+ override def toString: String = s"FIRST(${child}${if (ignoreNulls) "
IGNORE NULLS"})"
override def asPartial: SplitEvaluation = {
- val partialFirst = Alias(First(child), "PartialFirst")()
+ val partialFirst = Alias(First(child, ignoreNulls), "PartialFirst")()
SplitEvaluation(
- First(partialFirst.toAttribute),
+ First(partialFirst.toAttribute, ignoreNulls),
partialFirst :: Nil)
}
- override def newInstance(): FirstFunction = new FirstFunction(child,
this)
+ override def newInstance(): FirstFunction = new FirstFunction(child,
ignoreNulls, this)
}
-case class FirstFunction(expr: Expression, base: AggregateExpression1)
extends AggregateFunction1 {
- def this() = this(null, null) // Required for serialization.
+object First {
+ def apply(child: Expression): First = First(child, ignoreNulls = false)
+}
- var result: Any = null
+case class FirstFunction(
+ expr: Expression,
+ ignoreNulls: Boolean,
+ base: AggregateExpression1)
+ extends AggregateFunction1 {
+
+ def this() = this(null, null.asInstanceOf[Boolean], null) // Required
for serialization.
+
+ private[this] var result: Any = null
+
+ private[this] var valueSet: Boolean = false
override def update(input: InternalRow): Unit = {
- if (result == null) {
- result = expr.eval(input)
+ if (!valueSet) {
+ val value = expr.eval(input)
+ // When we have not set the result, we will set the result if we
respect nulls
+ // (i.e. ignoreNulls is false), or we ignore nulls and the evaluated
value is not null.
+ if (!ignoreNulls || (ignoreNulls && value != null)) {
+ result = value
+ valueSet = true
+ }
}
}
override def eval(input: InternalRow): Any = result
}
-case class Last(child: Expression) extends UnaryExpression with
PartialAggregate1 {
+case class Last(
+ child: Expression,
+ ignoreNulls: Boolean)
+ extends UnaryExpression with PartialAggregate1 {
+
+ def this(child: Expression) = this(child, false)
+
+ def this(child: Expression, ignoreNulls: Expression) = this(child,
ignoreNulls match {
+ case Literal(b: Boolean, BooleanType) => b
+ case _ =>
+ throw new AnalysisException("The second argument of Last should be a
boolean literal.")
+ })
+
override def references: AttributeSet = child.references
override def nullable: Boolean = true
override def dataType: DataType = child.dataType
- override def toString: String = s"LAST($child)"
+ override def toString: String = s"LAST($child)${if (ignoreNulls) "
IGNORE NULLS"}"
override def asPartial: SplitEvaluation = {
- val partialLast = Alias(Last(child), "PartialLast")()
+ val partialLast = Alias(Last(child, ignoreNulls), "PartialLast")()
SplitEvaluation(
- Last(partialLast.toAttribute),
+ Last(partialLast.toAttribute, ignoreNulls),
partialLast :: Nil)
}
- override def newInstance(): LastFunction = new LastFunction(child, this)
+ override def newInstance(): LastFunction = new LastFunction(child,
ignoreNulls, this)
}
-case class LastFunction(expr: Expression, base: AggregateExpression1)
extends AggregateFunction1 {
- def this() = this(null, null) // Required for serialization.
+object Last {
+ def apply(child: Expression): Last = Last(child, ignoreNulls = false)
+}
+
+case class LastFunction(
+ expr: Expression,
+ ignoreNulls: Boolean,
+ base: AggregateExpression1)
+ extends AggregateFunction1 {
+
+ def this() = this(null, null.asInstanceOf[Boolean], null) // Required
for serialization.
var result: Any = null
override def update(input: InternalRow): Unit = {
- result = input
+ val value = expr.eval(input)
+ if (ignoreNulls && value != null) {
+ result = value
+ } else {
--- End diff --
Both if and else and executing the same code.
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