org.apache.flink.table.api.dataview

Class MapView<K,V>

java.lang.Object

org.apache.flink.table.api.dataview.MapView<K,V>

All Implemented Interfaces:

Serializable, DataView

@TypeInfo(value=MapViewTypeInfoFactory.class)
 @PublicEvolving
public class MapView<K,V>
extends Object
implements DataView

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 state MapView which is backed by a MapState instead of HashMap if it works in streaming.

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 {

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
org.apache.flink.api.common.typeinfo.TypeInformation<?>	keyType
Map<K,V>	map
org.apache.flink.api.common.typeinfo.TypeInformation<?>	valueType

Constructor Summary

Constructors

Constructor and Description
MapView() Creates a MapView.
MapView(org.apache.flink.api.common.typeinfo.TypeInformation<?> keyType, org.apache.flink.api.common.typeinfo.TypeInformation<?> valueType) Creates a MapView with the specified key and value types.
MapView(org.apache.flink.api.common.typeinfo.TypeInformation<?> keyType, org.apache.flink.api.common.typeinfo.TypeInformation<?> valueType, Map<K,V> map)

Method Summary

Modifier and Type	Method and Description
void	clear() Removes all entries of this map.
boolean	contains(K key) Checks if the map view contains a value for a given key.
Iterable<Map.Entry<K,V>>	entries() Returns all entries of the map view.
boolean	equals(Object other)
V	get(K key) Return the value for the specified key or null if the key is not in the map view.
int	hashCode()
Iterator<Map.Entry<K,V>>	iterator() Returns an iterator over all entries of the map view.
Iterable<K>	keys() Returns all the keys in the map view.
void	put(K key, V value) Inserts a value for the given key into the map view.
void	putAll(Map<K,V> map) Inserts all mappings from the specified map to this map view.
void	remove(K key) Deletes the value for the given key.
Iterable<V>	values() Returns all the values in the map view.

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait

Field Detail

keyType

public transient org.apache.flink.api.common.typeinfo.TypeInformation<?> keyType

valueType

public transient org.apache.flink.api.common.typeinfo.TypeInformation<?> valueType

map

public final Map<K,V> map

Constructor Detail

MapView

public MapView(org.apache.flink.api.common.typeinfo.TypeInformation<?> keyType,
               org.apache.flink.api.common.typeinfo.TypeInformation<?> valueType,
               Map<K,V> map)

MapView

public MapView(org.apache.flink.api.common.typeinfo.TypeInformation<?> keyType,
               org.apache.flink.api.common.typeinfo.TypeInformation<?> valueType)

Creates a MapView with the specified key and value types.

Parameters:

keyType - The type of keys of the MapView.

valueType - The type of the values of the MapView.

MapView

public MapView()

Creates a MapView.

Method Detail

get

public V get(K key)
      throws Exception

Return the value for the specified key or null if the key is not in the map view.

Parameters:

key - The look up key.

Returns:

The value for the specified key.

Throws:

Exception - Thrown if the system cannot get data.

put

public void put(K key,
                V value)
         throws Exception

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.

Parameters:

key - The key for which the value is inserted.

value - The value that is inserted for the key.

Throws:

Exception - Thrown if the system cannot put data.

putAll

public void putAll(Map<K,V> map)
            throws Exception

Inserts all mappings from the specified map to this map view.

Parameters:

map - The map whose entries are inserted into this map view.

Throws:

Exception - Thrown if the system cannot access the map.

remove

public void remove(K key)
            throws Exception

Deletes the value for the given key.

Parameters:

key - The key for which the value is deleted.

Throws:

Exception - Thrown if the system cannot access the map.

contains

public boolean contains(K key)
                 throws Exception

Checks if the map view contains a value for a given key.

Parameters:

key - The key to check.

Returns:

True if there exists a value for the given key, false otherwise.

Throws:

Exception - Thrown if the system cannot access the map.

entries

public Iterable<Map.Entry<K,V>> entries()
                                 throws Exception

Returns all entries of the map view.

Returns:

An iterable of all the key-value pairs in the map view.

Throws:

Exception - Thrown if the system cannot access the map.

keys

public Iterable<K> keys()
                 throws Exception

Returns all the keys in the map view.

Returns:

An iterable of all the keys in the map.

Throws:

Exception - Thrown if the system cannot access the map.

values

public Iterable<V> values()
                   throws Exception

Returns all the values in the map view.

Returns:

An iterable of all the values in the map.

Throws:

Exception - Thrown if the system cannot access the map.

iterator

public Iterator<Map.Entry<K,V>> iterator()
                                  throws Exception

Returns an iterator over all entries of the map view.

Returns:

An iterator over all the mappings in the map.

Throws:

Exception - Thrown if the system cannot access the map.

clear

public void clear()

Removes all entries of this map.

Specified by:

clear in interface DataView

equals

public boolean equals(Object other)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object