[GitHub] [spark] erikerlandson commented on a change in pull request #25024: [SPARK-27296][SQL] User Defined Aggregators that do not ser/de on each input row

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erikerlandson commented on a change in pull request #25024: [SPARK-27296][SQL] User Defined Aggregators that do not ser/de on each input row
URL: https://github.com/apache/spark/pull/25024#discussion_r300840952
 
 

 ##########
 File path: sql/core/src/main/scala/org/apache/spark/sql/execution/aggregate/udaf.scala
 ##########
 @@ -450,3 +451,76 @@ case class ScalaUDAF(
 
   override def nodeName: String = udaf.getClass.getSimpleName
 }
+
+/**
+ * The internal wrapper used to hook a [[UserDefinedImperativeAggregator]] `udia` in the
+ * internal aggregation code path.
+ */
+case class ScalaUDIA[T](
+    children: Seq[Expression],
+    udia: UserDefinedImperativeAggregator[T],
+    mutableAggBufferOffset: Int = 0,
+    inputAggBufferOffset: Int = 0)
+  extends TypedImperativeAggregate[T]
+  with NonSQLExpression
+  with UserDefinedExpression
+  with ImplicitCastInputTypes
+  with Logging {
+
+  def dataType: DataType = udia.resultType
+
+  val inputTypes: Seq[DataType] = udia.inputSchema.map(_.dataType)
+
+  def nullable: Boolean = true
+
+  override lazy val deterministic: Boolean = udia.deterministic
+
+  def withNewMutableAggBufferOffset(newMutableAggBufferOffset: Int): ScalaUDIA[T] =
+    copy(mutableAggBufferOffset = newMutableAggBufferOffset)
+
+  def withNewInputAggBufferOffset(newInputAggBufferOffset: Int): ScalaUDIA[T] =
+    copy(inputAggBufferOffset = newInputAggBufferOffset)
+
+  private[this] lazy val childrenSchema: StructType = {
+    val inputFields = children.zipWithIndex.map {
+      case (child, index) =>
+        StructField(s"input$index", child.dataType, child.nullable, Metadata.empty)
+    }
+    StructType(inputFields)
+  }
+
+  private lazy val inputProjection = {
+    val inputAttributes = childrenSchema.toAttributes
+    log.debug(
+      s"Creating MutableProj: $children, inputSchema: $inputAttributes.")
+    MutableProjection.create(children, inputAttributes)
+  }
+
+  private[this] lazy val inputToScalaConverters: Any => Any =
+    CatalystTypeConverters.createToScalaConverter(childrenSchema)
+
+  def createAggregationBuffer(): T = udia.initial
+
+  def update(buffer: T, input: InternalRow): T = {
+    val inrow = inputToScalaConverters(inputProjection(input)).asInstanceOf[Row]
 
 Review comment:
   I'm not entirely sure what that conversion does. It appeared to be important for maintaining behavior equivalence with ScalaUDAF. If anyone with expertise in Catalyst has additional insight, I would be interested.

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