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From fhueske <...@git.apache.org>
Subject [GitHub] flink pull request #4585: [FLINK-7491] [Table API & SQL] add MultiSetTypeInf...
Date Thu, 21 Sep 2017 07:33:10 GMT
Github user fhueske commented on a diff in the pull request:

    https://github.com/apache/flink/pull/4585#discussion_r140167679
  
    --- Diff: flink-libraries/flink-table/src/main/scala/org/apache/flink/table/functions/aggfunctions/CollectAggFunction.scala
---
    @@ -0,0 +1,121 @@
    +/*
    + * 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.TypeInformation
    +import org.apache.flink.api.java.tuple.{Tuple1 => JTuple1}
    +import org.apache.flink.api.java.typeutils.{GenericTypeInfo, TupleTypeInfo}
    +import org.apache.flink.table.functions.AggregateFunction
    +
    +import scala.collection.JavaConverters._
    +
    +/** The initial accumulator for Collect aggregate function */
    +class CollectAccumulator[E] extends JTuple1[util.Map[E, Integer]]
    +
    +abstract class CollectAggFunction[E]
    +  extends AggregateFunction[util.Map[E, Integer], CollectAccumulator[E]] {
    +
    +  @transient
    +  private lazy val addFunction = new BiFunction[Integer, Integer, Integer] {
    +    override def apply(t: Integer, u: Integer): Integer = t + u
    +  }
    +
    +  override def createAccumulator(): CollectAccumulator[E] = {
    +    val acc = new CollectAccumulator[E]()
    +    acc.f0 = new util.HashMap[E, Integer]()
    +    acc
    +  }
    +
    +  def accumulate(accumulator: CollectAccumulator[E], value: E): Unit = {
    +    if (value != null) {
    +      if (accumulator.f0.containsKey(value)) {
    +        val add = (x: Integer, y: Integer) => x + y
    +        accumulator.f0.merge(value, 1, addFunction)
    +      } else {
    +        accumulator.f0.put(value, 1)
    +      }
    +    }
    +  }
    +
    +  override def getValue(accumulator: CollectAccumulator[E]): util.Map[E, Integer] = {
    +    if (accumulator.f0.size() > 0) {
    +      new util.HashMap(accumulator.f0)
    +    } else {
    +      null.asInstanceOf[util.Map[E, Integer]]
    +    }
    +  }
    +
    +  def resetAccumulator(acc: CollectAccumulator[E]): Unit = {
    +    acc.f0.clear()
    +  }
    +
    +  override def getAccumulatorType: TypeInformation[CollectAccumulator[E]] = {
    +    new TupleTypeInfo(
    +      classOf[CollectAccumulator[E]],
    +      new GenericTypeInfo[util.Map[E, Integer]](classOf[util.Map[E, Integer]]))
    --- End diff --
    
    We could have an abstract method `getElementTypeInfo()` that returns the type info for
the elements. The basic types can be properly handled and for `Object` we fall back to `GenericType`.


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