org.apache.flink.table.api.dataview.MapView.scala Maven / Gradle / Ivy
/*
* 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.api.dataview
import org.apache.flink.api.common.typeinfo.TypeInfo
import org.apache.flink.table.api.functions.AggregateFunction
import org.apache.flink.table.types.DataType
import org.apache.flink.table.typeutils.MapViewTypeInfoFactory
import java.lang.{Iterable => JIterable}
import java.util
/**
* A [[MapView]] provides Map functionality for accumulators used by user-defined aggregate
* functions [[AggregateFunction]].
*
* A [[MapView]] can be backed by a Java HashMap or a state backend, depending on the context in
* which the aggregation function is used.
*
* At runtime [[MapView]] will be replaced by a
* [[org.apache.flink.table.dataview.KeyedStateMapView]] if it is backed by a state backend.
*
* Example of an accumulator type with a [[MapView]] and an aggregate function that uses it:
* {{{
*
* public class MyAccum {
* public MapView map;
* public long count;
* }
*
* public class MyAgg extends AggregateFunction {
*
* @Override
* public MyAccum createAccumulator() {
* MyAccum accum = new MyAccum();
* accum.map = new MapView<>(Types.STRING, Types.INT);
* accum.count = 0L;
* return accum;
* }
*
* public void accumulate(MyAccum accumulator, String id) {
* try {
* if (!accumulator.map.contains(id)) {
* accumulator.map.put(id, 1);
* accumulator.count++;
* }
* } catch (Exception e) {
* e.printStackTrace();
* }
* }
*
* @Override
* public Long getValue(MyAccum accumulator) {
* return accumulator.count;
* }
* }
*
* }}}
*
* @param keyType key type
* @param valueType value type
* @tparam K key type
* @tparam V value type
*/
@TypeInfo(classOf[MapViewTypeInfoFactory[_, _]])
class MapView[K, V](
@transient private[flink] val keyType: DataType,
@transient private[flink] val valueType: DataType,
private[flink] val map: util.Map[K, V])
extends DataView {
/**
* Creates a MapView with the specified key and value types.
*
* @param keyType The type of keys of the MapView.
* @param valueType The type of the values of the MapView.
*/
def this(keyType: DataType, valueType: DataType) {
this(keyType, valueType, new util.HashMap[K, V]())
}
/**
* Creates a MapView.
*/
def this() = this(null, null)
/**
* Return the value for the specified key or { @code null } if the key is not in the map view.
*
* @param key The look up key.
* @return The value for the specified key.
* @throws Exception Thrown if the system cannot get data.
*/
@throws[Exception]
def get(key: K): V = map.get(key)
/**
* Inserts a value for the given key into the map view.
* If the map view already contains a value for the key, the existing value is overwritten.
*
* @param key The key for which the value is inserted.
* @param value The value that is inserted for the key.
* @throws Exception Thrown if the system cannot put data.
*/
@throws[Exception]
def put(key: K, value: V): Unit = map.put(key, value)
/**
* Inserts all mappings from the specified map to this map view.
*
* @param map The map whose entries are inserted into this map view.
* @throws Exception Thrown if the system cannot access the map.
*/
@throws[Exception]
def putAll(map: util.Map[K, V]): Unit = this.map.putAll(map)
/**
* Deletes the value for the given key.
*
* @param key The key for which the value is deleted.
* @throws Exception Thrown if the system cannot access the map.
*/
@throws[Exception]
def remove(key: K): Unit = map.remove(key)
/**
* Checks if the map view contains a value for a given key.
*
* @param key The key to check.
* @return True if there exists a value for the given key, false otherwise.
* @throws Exception Thrown if the system cannot access the map.
*/
@throws[Exception]
def contains(key: K): Boolean = map.containsKey(key)
/**
* Returns all entries of the map view.
*
* @return An iterable of all the key-value pairs in the map view.
* @throws Exception Thrown if the system cannot access the map.
*/
@throws[Exception]
def entries: JIterable[util.Map.Entry[K, V]] = map.entrySet()
/**
* Returns all the keys in the map view.
*
* @return An iterable of all the keys in the map.
* @throws Exception Thrown if the system cannot access the map.
*/
@throws[Exception]
def keys: JIterable[K] = map.keySet()
/**
* Returns all the values in the map view.
*
* @return An iterable of all the values in the map.
* @throws Exception Thrown if the system cannot access the map.
*/
@throws[Exception]
def values: JIterable[V] = map.values()
/**
* Returns an iterator over all entries of the map view.
*
* @return An iterator over all the mappings in the map.
* @throws Exception Thrown if the system cannot access the map.
*/
@throws[Exception]
def iterator: util.Iterator[util.Map.Entry[K, V]] = map.entrySet().iterator()
/**
* Removes all entries of this map.
*/
override def clear(): Unit = map.clear()
override def equals(other: Any): Boolean = other match {
case that: MapView[K, V] =>
map.equals(that.map)
case _ => false
}
override def hashCode(): Int = map.hashCode()
}