Type Parameters:

K - the type of key for this QueryCache

V - the type of value for this QueryCache
```
public interface QueryCache<K,V>
```
A concurrent, queryable data structure which is used to cache results of a continuous query executed on an IMap. It can be also thought of as an always up to date view or snapshot of the IMap. Typically, QueryCache is used for performance reasons. This QueryCache can be configured via QueryCacheConfig. It can be reached like this:
```
 

     IMap map = hzInstance.getMap("mapName");
     Predicate predicate = TruePredicate.INSTANCE;
     QueryCache cache = map.getQueryCache(cacheId, predicate, includeValue);

 
 
```
This cache is evictable. The eviction can be configured with QueryCacheConfig.setEvictionConfig(com.hazelcast.config.EvictionConfig). Events caused by IMap eviction are not reflected to this cache. But the events published after an explicit call to IMap.evict(K) are reflected to this cache.
GOTCHAS
- This QueryCache implementation relies on the eventing system, if a listener is attached to this QueryCache it may receive same event more than once in case of a system failure. Check out tryRecover()
- All writes to this QueryCache is reflected to underlying IMap and that write operation will eventually be reflected to this QueryCache after receiving the event of that operation.
- Currently, updates performed on the entries are reflected in the indexes in a non-atomic way. Therefore, if there are indexes configured for the query cache, their state may slightly lag behind the state of the entries. Use map listeners if you need to observe the state when the entry store and its indexes are consistent about the state of a particular entry, see addEntryListener for more details.
- There are some gotchas same with underlying IMap implementation, one should take care of them before using this QueryCache. Please check gotchas section in IMap class for them.
Since:

3.5

See Also:

QueryCacheConfig

Method Summary

All Methods Instance Methods Abstract Methods Default Methods
Modifier and Type	Method	Description
`java.util.UUID`	`addEntryListener(MapListener listener, boolean includeValue)`
`java.util.UUID`	`addEntryListener(MapListener listener, Predicate<K,V> predicate, boolean includeValue)`
`java.util.UUID`	`addEntryListener(MapListener listener, Predicate<K,V> predicate, K key, boolean includeValue)`
`java.util.UUID`	`addEntryListener(MapListener listener, K key, boolean includeValue)`
`void`	`addIndex(IndexConfig config)`
`default void`	`addIndex(IndexType type, java.lang.String... attributes)`
`boolean`	`containsKey(java.lang.Object key)`
`boolean`	`containsValue(java.lang.Object value)`
`void`	`destroy()`	Destroys this cache.
`java.util.Set<java.util.Map.Entry<K,V>>`	`entrySet()`
`java.util.Set<java.util.Map.Entry<K,V>>`	`entrySet(Predicate<K,V> predicate)`
`V`	`get(java.lang.Object key)`
`java.util.Map<K,V>`	`getAll(java.util.Set<K> keys)`
`java.lang.String`	`getName()`	Returns the name of this `QueryCache`.
`boolean`	`isEmpty()`
`java.util.Set<K>`	`keySet()`
`java.util.Set<K>`	`keySet(Predicate<K,V> predicate)`
`boolean`	`removeEntryListener(java.util.UUID id)`
`int`	`size()`
`boolean`	`tryRecover()`	This method can be used to recover from a possible event loss situation.
`java.util.Collection<V>`	`values()`
`java.util.Collection<V>`	`values(Predicate<K,V> predicate)`

- Method Detail
  - get
```
V get(java.lang.Object key)
```
    See Also:
    
    IMap.get(Object)
  - containsKey
```
boolean containsKey(java.lang.Object key)
```
    See Also:
    
    IMap.containsKey(Object)
  - containsValue
```
boolean containsValue(java.lang.Object value)
```
    See Also:
    
    IMap.containsValue(Object)
  - isEmpty
```
boolean isEmpty()
```
    See Also:
    
    Map.isEmpty()
  - size
```
int size()
```
    See Also:
    
    Map.size()
  - addIndex
```
default void addIndex(IndexType type,
                      java.lang.String... attributes)
```
    See Also:
    
    IMap.addIndex(IndexType, String...)
  - addIndex
```
void addIndex(IndexConfig config)
```
    See Also:
    
    IMap.addIndex(IndexConfig)
  - getAll
```
java.util.Map<K,V> getAll(java.util.Set<K> keys)
```
    See Also:
    
    IMap.getAll(Set)
  - keySet
```
java.util.Set<K> keySet()
```
    See Also:
    
    IMap.keySet()
  - values
```
java.util.Collection<V> values()
```
    See Also:
    
    IMap.values()
  - entrySet
```
java.util.Set<java.util.Map.Entry<K,V>> entrySet()
```
    See Also:
    
    IMap.entrySet()
  - keySet
```
java.util.Set<K> keySet(Predicate<K,V> predicate)
```
    See Also:
    
    IMap.keySet(Predicate)
  - values
```
java.util.Collection<V> values(Predicate<K,V> predicate)
```
    See Also:
    
    IMap.values(Predicate)
  - entrySet
```
java.util.Set<java.util.Map.Entry<K,V>> entrySet(Predicate<K,V> predicate)
```
    See Also:
    
    IMap.entrySet(Predicate)
  - addEntryListener
```
java.util.UUID addEntryListener(MapListener listener,
                                boolean includeValue)
```
    See Also:
    
    IMap.addEntryListener(MapListener, boolean)
  - addEntryListener
```
java.util.UUID addEntryListener(MapListener listener,
                                K key,
                                boolean includeValue)
```
    See Also:
    
    IMap.addEntryListener(MapListener, Object, boolean)
  - addEntryListener
```
java.util.UUID addEntryListener(MapListener listener,
                                Predicate<K,V> predicate,
                                boolean includeValue)
```
    See Also:
    
    IMap.addEntryListener(MapListener, Predicate, boolean)
  - addEntryListener
```
java.util.UUID addEntryListener(MapListener listener,
                                Predicate<K,V> predicate,
                                K key,
                                boolean includeValue)
```
    See Also:
    
    IMap.addEntryListener(MapListener, Predicate, Object, boolean)
  - removeEntryListener
```
boolean removeEntryListener(java.util.UUID id)
```
    See Also:
    
    IMap.removeEntryListener(UUID)
  - getName
```
java.lang.String getName()
```
    Returns the name of this QueryCache. The returned value will never be null.
    
    Returns:
    
    the name of this QueryCache.
  - tryRecover
```
boolean tryRecover()
```
    This method can be used to recover from a possible event loss situation. You can detect event loss via EventLostListener
    This method tries to make consistent the data in this QueryCache with the data in the underlying IMap by replaying the events after last consistently received ones. As a result of this replaying logic, same event may appear more than once to the QueryCache listeners.
    This method returns false if the event is not in the buffer of event publisher side. That means recovery is not possible.
    
    Returns:
    
    true if the QueryCache content will be eventually consistent, otherwise false.
    
    See Also:
    
    QueryCacheConfig.bufferSize
  - destroy
```
void destroy()
```
    Destroys this cache. Clears and releases all local and remote resources created for this cache.

Interface QueryCache<K,​V>

Method Summary

Method Detail

get

containsKey

containsValue

isEmpty

size

addIndex

addIndex

getAll

keySet

values

entrySet

keySet

values

entrySet

addEntryListener

addEntryListener

addEntryListener

addEntryListener

removeEntryListener

getName

tryRecover

destroy

Interface QueryCache<K,V>