[SPARK-16200][SQL] Rename AggregateFunction#supportsPartial

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/aggregate/collect.scala

@@ -45,7 +45,7 @@ abstract class Collect extends ImperativeAggregate {
 
   override def inputTypes: Seq[AbstractDataType] = Seq(AnyDataType)
 
-  override def supportsPartial: Boolean = false
+  override def forceSortAggregate: Boolean = true
 
   override def aggBufferAttributes: Seq[AttributeReference] = Nil
 

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/aggregate/interfaces.scala

@@ -174,10 +174,10 @@ sealed abstract class AggregateFunction extends Expression with ImplicitCastInpu
   def inputAggBufferAttributes: Seq[AttributeReference]
 
   /**
-   * Indicates if this function supports partial aggregation.
-   * Currently Hive UDAF is the only one that doesn't support partial aggregation.
+   * Indicates if this function needs to aggregate values group-by-group in a single step.
+   * If true, we must always use a `SortAggregateExec` operator without partial aggregates.
    */
-  def supportsPartial: Boolean = true
+  def forceSortAggregate: Boolean = false
 
   /**
    * Result of the aggregate function when the input is empty. This is currently only used for the

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/windowExpressions.scala

@@ -431,7 +431,7 @@ abstract class AggregateWindowFunction extends DeclarativeAggregate with WindowF
   override val frame = SpecifiedWindowFrame(RowFrame, UnboundedPreceding, CurrentRow)
   override def dataType: DataType = IntegerType
   override def nullable: Boolean = true
-  override def supportsPartial: Boolean = false
+  override def forceSortAggregate: Boolean = true
   override lazy val mergeExpressions =
     throw new UnsupportedOperationException("Window Functions do not support merging.")
 }

sql/core/src/main/scala/org/apache/spark/sql/execution/SparkStrategies.scala

@@ -261,7 +261,7 @@ private[sql] abstract class SparkStrategies extends QueryPlanner[SparkPlan] {
         }
 
         val aggregateOperator =
-          if (aggregateExpressions.map(_.aggregateFunction).exists(!_.supportsPartial)) {
+          if (aggregateExpressions.map(_.aggregateFunction).exists(_.forceSortAggregate)) {
             if (functionsWithDistinct.nonEmpty) {
               sys.error("Distinct columns cannot exist in Aggregate operator containing " +
                 "aggregate functions which don't support partial aggregation.")

sql/hive/src/main/scala/org/apache/spark/sql/hive/hiveUDFs.scala

@@ -336,7 +336,7 @@ private[hive] case class HiveUDAFFunction(
 
   override def nullable: Boolean = true
 
-  override def supportsPartial: Boolean = false
+  override def forceSortAggregate: Boolean = true
 
   override lazy val dataType: DataType = inspectorToDataType(returnInspector)