Github user twalthr commented on a diff in the pull request:
https://github.com/apache/flink/pull/3150#discussion_r96606158
--- Diff:
flink-libraries/flink-table/src/main/scala/org/apache/flink/table/runtime/aggregate/DataSetSessionWindowAggregateCombineGroupFunction.scala
---
@@ -0,0 +1,133 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.flink.table.runtime.aggregate
+
+import java.lang.Iterable
+
+import org.apache.flink.api.common.functions.RichGroupCombineFunction
+import org.apache.flink.api.common.typeinfo.TypeInformation
+import org.apache.flink.api.java.typeutils.ResultTypeQueryable
+import org.apache.flink.types.Row
+import org.apache.flink.configuration.Configuration
+import org.apache.flink.util.{Collector, Preconditions}
+
+import scala.collection.JavaConversions._
+
+/**
+ * This wraps the aggregate logic inside of
+ * [[org.apache.flink.api.java.operators.GroupCombineOperator]].
+ *
+ * @param aggregates The aggregate functions.
+ * @param groupingKeys
+ * @param intermediateRowArity The intermediate row field count.
+ * @param gap Session time window gap.
+ * @param intermediateRowType Intermediate row data type.
+ */
+class DataSetSessionWindowAggregateCombineGroupFunction(
+ aggregates: Array[Aggregate[_ <: Any]],
+ groupingKeys: Array[Int],
+ intermediateRowArity: Int,
+ gap: Long,
+ @transient intermediateRowType: TypeInformation[Row])
+ extends RichGroupCombineFunction[Row,Row] with ResultTypeQueryable[Row] {
+
+ private var aggregateBuffer: Row = _
+ private var rowTimePos = 0
+
+ override def open(config: Configuration) {
+ Preconditions.checkNotNull(aggregates)
+ Preconditions.checkNotNull(groupingKeys)
+ aggregateBuffer = new Row(intermediateRowArity)
+ rowTimePos = intermediateRowArity - 2
+ }
+
+ /**
+ * For sub-grouped intermediate aggregate Rows, divide window based on
the row-time
+ * (current'row-time - previousârow-time > gap), and then merge data
(within a unified window)
+ * into an aggregate buffer.
+ *
+ * @param records Sub-grouped intermediate aggregate Rows .
+ * @return Combined intermediate aggregate Row.
+ *
+ */
+ override def combine(
+ records: Iterable[Row],
+ out: Collector[Row]): Unit = {
+
+ var head:Row = null
+ var lastRowTime: Option[Long] = None
+ var currentRowTime: Option[Long] = None
+
+ records.foreach(
+ (record) => {
+ currentRowTime =
Some(record.getField(rowTimePos).asInstanceOf[Long])
--- End diff --
We should not use Scala magic here. I don't know how `Option` is
implemented but this `Some` could create objects for every record at runtime
which is not very efficient. I recommend to use `null` here.
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