Github user fhueske commented on a diff in the pull request:
https://github.com/apache/flink/pull/3470#discussion_r104394062
--- Diff:
flink-libraries/flink-table/src/main/scala/org/apache/flink/table/functions/aggfunctions/SumWithRetractAggFunction.scala
---
@@ -0,0 +1,201 @@
+/*
+ * 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.functions.aggfunctions
+
+import java.math.BigDecimal
+import java.util.{List => JList}
+
+import org.apache.flink.api.common.typeinfo.{BasicTypeInfo,
TypeInformation}
+import org.apache.flink.api.java.tuple.{Tuple2 => JTuple2}
+import org.apache.flink.api.java.typeutils.TupleTypeInfo
+import org.apache.flink.table.api.TableException
+import org.apache.flink.table.functions.{Accumulator, AggregateFunction}
+
+/** The initial accumulator for Sum with retract aggregate function */
+class SumWithRetractAccumulator[T] extends JTuple2[T, Long] with
Accumulator
+
+/**
+ * Base class for built-in Sum with retract aggregate function
+ *
+ * @tparam T the type for the aggregation result
+ */
+abstract class SumWithRetractAggFunction[T: Numeric] extends
AggregateFunction[T] {
+
+ private val numeric = implicitly[Numeric[T]]
+
+ override def createAccumulator(): Accumulator = {
+ val acc = new SumWithRetractAccumulator[T]()
+ acc.f0 = numeric.zero //sum
+ acc.f1 = 0L //total count
+ acc
+ }
+
+ override def accumulate(accumulator: Accumulator, value: Any): Unit = {
+ if (value != null) {
+ val v = value.asInstanceOf[T]
+ val a = accumulator.asInstanceOf[SumWithRetractAccumulator[T]]
+ a.f0 = numeric.plus(a.f0, v)
+ a.f1 += 1
+ }
+ }
+
+ override def retract(accumulator: Accumulator, value: Any): Unit = {
+ if (value != null) {
+ val v = value.asInstanceOf[T]
+ val a = accumulator.asInstanceOf[SumWithRetractAccumulator[T]]
+ a.f0 = numeric.minus(a.f0, v)
+ a.f1 -= 1
+ }
+ }
+
+ override def getValue(accumulator: Accumulator): T = {
+ val a = accumulator.asInstanceOf[SumWithRetractAccumulator[T]]
+ if (a.f1 > 0) {
+ a.f0
+ } else {
+ null.asInstanceOf[T]
+ }
+ }
+
+ override def merge(accumulators: JList[Accumulator]): Accumulator = {
+ val ret =
createAccumulator().asInstanceOf[SumWithRetractAccumulator[T]]
+ var i: Int = 0
+ while (i < accumulators.size()) {
+ val a =
accumulators.get(i).asInstanceOf[SumWithRetractAccumulator[T]]
+ ret.f0 = numeric.plus(ret.f0, a.f0)
+ ret.f1 += a.f1
+ i += 1
+ }
+ ret
+ }
+
+ override def getAccumulatorType(): TypeInformation[_] = {
+ new TupleTypeInfo(
+ (new SumWithRetractAccumulator).getClass,
+ getValueTypeInfo,
+ BasicTypeInfo.LONG_TYPE_INFO)
+ }
+
+ def getValueTypeInfo: TypeInformation[_]
+}
+
+/**
+ * Built-in Byte Sum with retract aggregate function
+ */
+class ByteSumWithRetractAggFunction extends
SumWithRetractAggFunction[Byte] {
+ override def getValueTypeInfo = BasicTypeInfo.BYTE_TYPE_INFO
+}
+
+/**
+ * Built-in Short Sum with retract aggregate function
+ */
+class ShortSumWithRetractAggFunction extends
SumWithRetractAggFunction[Short] {
+ override def getValueTypeInfo = BasicTypeInfo.SHORT_TYPE_INFO
+}
+
+/**
+ * Built-in Int Sum with retract aggregate function
+ */
+class IntSumWithRetractAggFunction extends SumWithRetractAggFunction[Int] {
+ override def getValueTypeInfo = BasicTypeInfo.INT_TYPE_INFO
+}
+
+/**
+ * Built-in Long Sum with retract aggregate function
+ */
+class LongSumWithRetractAggFunction extends
SumWithRetractAggFunction[Long] {
+ override def getValueTypeInfo = BasicTypeInfo.LONG_TYPE_INFO
+}
+
+/**
+ * Built-in Float Sum with retract aggregate function
+ */
+class FloatSumWithRetractAggFunction extends
SumWithRetractAggFunction[Float] {
+ override def getValueTypeInfo = BasicTypeInfo.FLOAT_TYPE_INFO
+}
+
+/**
+ * Built-in Double Sum with retract aggregate function
+ */
+class DoubleSumWithRetractAggFunction extends
SumWithRetractAggFunction[Double] {
+ override def getValueTypeInfo = BasicTypeInfo.DOUBLE_TYPE_INFO
+}
+
+/** The initial accumulator for Big Decimal Sum with retract aggregate
function */
+class DecimalSumWithRetractAccumulator extends JTuple2[BigDecimal, Long]
with Accumulator {
+ f0 = BigDecimal.ZERO
+ f1 = 0L
+}
+
+/**
+ * Built-in Big Decimal Sum with retract aggregate function
+ */
+class DecimalSumWithRetractAggFunction extends
AggregateFunction[BigDecimal] {
+
+ override def createAccumulator(): Accumulator = {
+ new DecimalSumWithRetractAccumulator
+ }
+
+ override def accumulate(accumulator: Accumulator, value: Any): Unit = {
+ if (value != null) {
+ val v = value.asInstanceOf[BigDecimal]
+ val accum =
accumulator.asInstanceOf[DecimalSumWithRetractAccumulator]
+ accum.f0 = accum.f0.add(v)
+ accum.f1 += 1L
+ }
+ }
+
+ override def retract(accumulator: Accumulator, value: Any): Unit = {
+ if (value != null) {
+ val v = value.asInstanceOf[BigDecimal]
+ val accum =
accumulator.asInstanceOf[DecimalSumWithRetractAccumulator]
+ accum.f0 = accum.f0.subtract(v)
+ accum.f1 -= 1L
+ if (accum.f1 == 0) {
--- End diff --
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