Github user fhueske commented on a diff in the pull request:
https://github.com/apache/flink/pull/3354#discussion_r102241426
--- Diff:
flink-libraries/flink-table/src/main/scala/org/apache/flink/table/functions/builtInAggFuncs/AvgAggFunction.scala
---
@@ -0,0 +1,268 @@
+/*
+ * 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.builtInAggFuncs
+
+import java.math.{BigDecimal, BigInteger}
+import org.apache.flink.table.functions.{Accumulator, AggregateFunction}
+
+/**
+ * Base class for built-in Integral Avg aggregate function
+ *
+ * @tparam T the type for the aggregation result
+ */
+abstract class IntegralAvgAggFunction[T] extends AggregateFunction[T] {
+ /** The initial accumulator for Integral Avg aggregate function */
+ class IntegralAvgAccumulator extends Accumulator {
+ var sum: Long = 0
+ var count: Long = 0
+ }
+
+ override def createAccumulator(): Accumulator = {
+ new IntegralAvgAccumulator
+ }
+
+ override def accumulate(accumulator: Accumulator, value: Any) = {
+ if (value != null) {
+ val v = value.asInstanceOf[Number].longValue()
+ val accum = accumulator.asInstanceOf[IntegralAvgAccumulator]
+ accum.sum += v
+ accum.count += 1
+ }
+ }
+
+ override def getValue(accumulator: Accumulator): T = {
+ val accum = accumulator.asInstanceOf[IntegralAvgAccumulator]
+ val sum = accum.sum
+ if (accum.count == 0) {
+ null.asInstanceOf[T]
+ } else {
+ resultTypeConvert(accum.sum / accum.count)
+ }
+ }
+
+ override def merge(a: Accumulator, b: Accumulator): Accumulator = {
+ val aAccum = a.asInstanceOf[IntegralAvgAccumulator]
+ val bAccum = b.asInstanceOf[IntegralAvgAccumulator]
+ aAccum.count += bAccum.count
+ aAccum.sum += bAccum.sum
+ a
+ }
+ /**
+ * Convert the intermediate result to the expected aggregation result
type
+ *
+ * @param value the intermediate result. We use a Long container to save
+ * the intermediate result to avoid the overflow by sum
operation.
+ * @return the result value with the expected aggregation result type
+ */
+ def resultTypeConvert(value: Long): T
+}
+
+/**
+ * Built-in Byte Avg aggregate function
+ */
+class ByteAvgAggFunction extends IntegralAvgAggFunction[Byte] {
+ override def resultTypeConvert(value: Long): Byte = value.toByte
+}
+
+/**
+ * Built-in Short Avg aggregate function
+ */
+class ShortAvgAggFunction extends IntegralAvgAggFunction[Short] {
+ override def resultTypeConvert(value: Long): Short = value.toShort
+}
+
+/**
+ * Built-in Int Avg aggregate function
+ */
+class IntAvgAggFunction extends IntegralAvgAggFunction[Int] {
+ override def resultTypeConvert(value: Long): Int = value.toInt
+}
+
+/**
+ * Base Class for Built-in Big Integral Avg aggregate function
+ *
+ * @tparam T the type for the aggregation result
+ */
+abstract class BigIntegralAvgAggFunction[T] extends AggregateFunction[T] {
+ /** The initial accumulator for Big Integral Avg aggregate function */
+ class BigIntegralAvgAccumulator extends Accumulator {
+ var sum: BigInteger = BigInteger.ZERO
+ var count: Long = 0
+ }
+
+ override def createAccumulator(): Accumulator = {
+ new BigIntegralAvgAccumulator
+ }
+
+ override def accumulate(accumulator: Accumulator, value: Any) = {
+ if (value != null) {
+ val v = value.asInstanceOf[Long]
+ val accum = accumulator.asInstanceOf[BigIntegralAvgAccumulator]
+ accum.sum = accum.sum.add(BigInteger.valueOf(v))
+ accum.count += 1
+ }
+ }
+
+ override def getValue(accumulator: Accumulator): T = {
+ val accum = accumulator.asInstanceOf[BigIntegralAvgAccumulator]
+ val sum = accum.sum
+ if (accum.count == 0) {
+ null.asInstanceOf[T]
+ } else {
+ resultTypeConvert(accum.sum.divide(BigInteger.valueOf(accum.count)))
+ }
+ }
+
+ override def merge(a: Accumulator, b: Accumulator): Accumulator = {
+ val aAccum = a.asInstanceOf[BigIntegralAvgAccumulator]
+ val bAccum = b.asInstanceOf[BigIntegralAvgAccumulator]
+ aAccum.count += bAccum.count
+ aAccum.sum = aAccum.sum.add(bAccum.sum)
+ a
+ }
+
+ /**
+ * Convert the intermediate result to the expected aggregation result
type
+ *
+ * @param value the intermediate result. We use a BigInteger container
to
+ * save the intermediate result to avoid the overflow by sum
+ * operation.
+ * @return the result value with the expected aggregation result type
+ */
+ def resultTypeConvert(value: BigInteger): T
+}
+
+/**
+ * Built-in Long Avg aggregate function
+ */
+class LongAvgAggFunction extends BigIntegralAvgAggFunction[Long] {
+ override def resultTypeConvert(value: BigInteger): Long =
value.longValue()
+}
+
+/**
+ * Base class for built-in Floating Avg aggregate function
+ *
+ * @tparam T the type for the aggregation result
+ */
+abstract class FloatingAvgAggFunction[T] extends AggregateFunction[T] {
+ /** The initial accumulator for Floating Avg aggregate function */
+ class FloatingAvgAccumulator extends Accumulator {
+ var sum: Double = 0
+ var count: Long = 0
+ }
+
+ override def createAccumulator(): Accumulator = {
+ new FloatingAvgAccumulator
+ }
+
+ override def accumulate(accumulator: Accumulator, value: Any) = {
+ if (value != null) {
+ val v = value.asInstanceOf[Number].doubleValue()
+ val accum = accumulator.asInstanceOf[FloatingAvgAccumulator]
+ accum.sum += v
+ accum.count += 1
+ }
+ }
+
+ override def getValue(accumulator: Accumulator): T = {
+ val accum = accumulator.asInstanceOf[FloatingAvgAccumulator]
+ val sum = accum.sum
+ if (accum.count == 0) {
+ null.asInstanceOf[T]
+ } else {
+ resultTypeConvert(accum.sum / accum.count)
+ }
+ }
+
+ override def merge(a: Accumulator, b: Accumulator): Accumulator = {
+ val aAccum = a.asInstanceOf[FloatingAvgAccumulator]
+ val bAccum = b.asInstanceOf[FloatingAvgAccumulator]
+ aAccum.count += bAccum.count
+ aAccum.sum += bAccum.sum
+ a
+ }
+
+ /**
+ * Convert the intermediate result to the expected aggregation result
type
+ *
+ * @param value the intermediate result. We use a Double container to
save
+ * the intermediate result to avoid the overflow by sum
operation.
+ * @return the result value with the expected aggregation result type
+ */
+ def resultTypeConvert(value: Double): T
+}
+
+/**
+ * Built-in Float Avg aggregate function
+ */
+class FloatAvgAggFunction extends FloatingAvgAggFunction[Float] {
+ override def resultTypeConvert(value: Double): Float = value.toFloat
+}
+
+/**
+ * Built-in Int Double aggregate function
+ */
+class DoubleAvgAggFunction extends FloatingAvgAggFunction[Double] {
+ override def resultTypeConvert(value: Double): Double = value
+}
+
+/**
+ * Base class for built-in Big Decimal Avg aggregate function
+ */
+class DecimalAvgAggFunction extends AggregateFunction[BigDecimal] {
+ /** The initial accumulator for Big Decimal Avg aggregate function */
+ class DecimalAvgAccumulator extends Accumulator {
+ var sum: BigDecimal = null
+ var count: Long = 0
+ }
+
+ override def createAccumulator(): Accumulator = {
+ new DecimalAvgAccumulator
+ }
+
+ override def accumulate(accumulator: Accumulator, value: Any) = {
+ if (value != null) {
+ val v = value.asInstanceOf[BigDecimal]
+ val accum = accumulator.asInstanceOf[DecimalAvgAccumulator]
+ accum.count += 1
+ if (accum.sum == null) {
+ accum.sum = v
+ } else {
+ accum.sum = accum.sum.add(v)
+ }
+ }
+ }
+
+ override def getValue(accumulator: Accumulator): BigDecimal = {
+ val sum = accumulator.asInstanceOf[DecimalAvgAccumulator].sum
+ val count = accumulator.asInstanceOf[DecimalAvgAccumulator].count
+ if (sum == null || count == 0) {
+ null.asInstanceOf[BigDecimal]
+ } else {
+ sum.divide(BigDecimal.valueOf(count))
+ }
+ }
+
+ override def merge(a: Accumulator, b: Accumulator): Accumulator = {
+ val aAccum = a.asInstanceOf[DecimalAvgAccumulator]
+ val bAccum = b.asInstanceOf[DecimalAvgAccumulator]
+ aAccum.count += bAccum.count
+ accumulate(a, b.asInstanceOf[DecimalAvgAccumulator].sum)
--- End diff --
Won't `count` be off by one because `accumulate` will increment `count` as
well?
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