Github user suez1224 commented on a diff in the pull request:
https://github.com/apache/flink/pull/4585#discussion_r141507401
--- Diff:
flink-libraries/flink-table/src/main/scala/org/apache/flink/table/functions/aggfunctions/CollectAggFunction.scala
---
@@ -0,0 +1,158 @@
+/*
+ * 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.lang.{Iterable => JIterable}
+import java.util
+import java.util.function.BiFunction
+
+import org.apache.flink.api.common.typeinfo.{BasicTypeInfo,
TypeInformation}
+import org.apache.flink.api.java.typeutils._
+import org.apache.flink.table.api.dataview.MapView
+import org.apache.flink.table.dataview.MapViewTypeInfo
+import org.apache.flink.table.functions.AggregateFunction
+
+
+/** The initial accumulator for Collect aggregate function */
+class CollectAccumulator[E](var f0:MapView[E, Integer]) {
+ def this() {
+ this(null)
+ }
+
+ def canEqual(a: Any) = a.isInstanceOf[CollectAccumulator[E]]
+
+ override def equals(that: Any): Boolean =
+ that match {
+ case that: CollectAccumulator[E] => that.canEqual(this) && this.f0
== that.f0
+ case _ => false
+ }
+}
+
+abstract class CollectAggFunction[E]
+ extends AggregateFunction[util.Map[E, Integer], CollectAccumulator[E]] {
+
+ override def createAccumulator(): CollectAccumulator[E] = {
+ val acc = new CollectAccumulator[E](new MapView[E, Integer](
+ getValueTypeInfo.asInstanceOf[TypeInformation[E]],
BasicTypeInfo.INT_TYPE_INFO))
+ acc
+ }
+
+ def accumulate(accumulator: CollectAccumulator[E], value: E): Unit = {
+ if (value != null) {
+ if (accumulator.f0.contains(value)) {
+ accumulator.f0.put(value, accumulator.f0.get(value) + 1)
+ } else {
+ accumulator.f0.put(value, 1)
+ }
+ }
+ }
+
+ override def getValue(accumulator: CollectAccumulator[E]): util.Map[E,
Integer] = {
+ val iterator = accumulator.f0.iterator
+ if (iterator.hasNext) {
+ val map = new util.HashMap[E, Integer]()
+ while (iterator.hasNext) {
+ val entry = iterator.next()
+ map.put(entry.getKey, entry.getValue)
+ }
+ map
+ } else {
+ null.asInstanceOf[util.Map[E, Integer]]
--- End diff --
Check with Calcite tests, should return an empty Multiset instead.
---
