public final class ContinuousQuery<K,V> extends AbstractContinuousQuery<K,V>
Continuous queries allow registering a remote filter and a local listener for cache updates. If an update event passes the filter, it will be sent to the node that executed the query, and local listener will be notified.
Additionally, you can execute an initial query to get currently existing data.
Query can be of any type (SQL, TEXT or SCAN) and can be set via setInitialQuery(Query)
method.
Query can be executed either on all nodes in topology using IgniteCache.query(Query)
method, or only on the local node, if Query.setLocal(boolean) parameter is set to true.
Note that if the query is distributed and a new node joins, it will get the remote
filter for the query during discovery process before it actually joins a topology,
so no updates will be missed.
'Person' objects and we need
to query for all people with salary above 1000.
Here is the Person class:
public class Person {
// Name.
private String name;
// Salary.
private double salary;
...
}
You can create and execute a continuous query like so:
// Create a new continuous query.
ContinuousQuery<Long, Person> qry = new ContinuousQuery<>();
// Initial iteration query will return all people with salary above 1000.
qry.setInitialQuery(new ScanQuery<>((id, p) -> p.getSalary() > 1000));
// Callback that is called locally when update notifications are received.
// It simply prints out information about all created or modified records.
qry.setLocalListener((evts) -> {
for (CacheEntryEvent<? extends Long, ? extends Person> e : evts) {
Person p = e.getValue();
System.out.println(p.getFirstName() + " " + p.getLastName() + "'s salary is " + p.getSalary());
}
});
// The continuous listener will be notified for people with salary above 1000.
qry.setRemoteFilter(evt -> evt.getValue().getSalary() > 1000);
// Execute the query and get a cursor that iterates through the initial data.
QueryCursor<Cache.Entry<Long, Person>> cur = cache.query(qry);
This will execute query on all nodes that have the cache you are working with and
listener will start receiving notifications for cache updates.
To stop receiving updates call QueryCursor.close() method:
cur.close();Note that this works even if you didn't provide the initial query. Cursor will be empty in this case, but it will still unregister listeners when
QueryCursor.close()
is called.
IgniteAsyncCallback annotation is supported for CacheEntryEventFilter
(see AbstractContinuousQuery.setRemoteFilterFactory(Factory)) and CacheEntryUpdatedListener
(see setLocalListener(CacheEntryUpdatedListener)).
If a filter and/or listener are annotated with IgniteAsyncCallback then the annotated callback
is executed in an async callback pool (see IgniteConfiguration.getAsyncCallbackPoolSize())
and a notification order is kept the same as an update order for a given cache key.
DFLT_AUTO_UNSUBSCRIBE, DFLT_PAGE_SIZE, DFLT_TIME_INTERVAL| Constructor and Description |
|---|
ContinuousQuery()
Creates new continuous query.
|
| Modifier and Type | Method and Description |
|---|---|
javax.cache.event.CacheEntryUpdatedListener<K,V> |
getLocalListener() |
CacheEntryEventSerializableFilter<K,V> |
getRemoteFilter()
Gets remote filter.
|
ContinuousQuery<K,V> |
setAutoUnsubscribe(boolean autoUnsubscribe)
Sets automatic unsubscribe flag.
|
ContinuousQuery<K,V> |
setInitialQuery(Query<javax.cache.Cache.Entry<K,V>> initQry)
Sets initial query.
|
ContinuousQuery<K,V> |
setLocal(boolean loc)
Sets whether this query should be executed on a local node only.
|
ContinuousQuery<K,V> |
setLocalListener(javax.cache.event.CacheEntryUpdatedListener<K,V> locLsnr)
Sets a local callback.
|
ContinuousQuery<K,V> |
setPageSize(int pageSize)
Sets optional page size, if
0, then default is used. |
ContinuousQuery<K,V> |
setRemoteFilter(CacheEntryEventSerializableFilter<K,V> rmtFilter)
Deprecated.
|
ContinuousQuery<K,V> |
setTimeInterval(long timeInterval)
Sets time interval.
|
getInitialQuery, getRemoteFilterFactory, getTimeInterval, isAutoUnsubscribe, isIncludeExpired, setIncludeExpired, setRemoteFilterFactorygetPageSize, isLocal, prepare, toStringpublic ContinuousQuery<K,V> setInitialQuery(Query<javax.cache.Cache.Entry<K,V>> initQry)
This query will be executed before continuous listener is registered which allows to iterate through entries which already existed at the time continuous query is executed.
setInitialQuery in class AbstractContinuousQuery<K,V>initQry - Initial query.this for chaining.public ContinuousQuery<K,V> setLocalListener(javax.cache.event.CacheEntryUpdatedListener<K,V> locLsnr)
The callback predicate accepts ID of the node from where updates are received and a collection
of the received entries. Note that for removed entries values will be null.
If the predicate returns false, query execution will be cancelled.
WARNING: all operations that involve any kind of JVM-local or distributed locking (e.g., synchronization or transactional cache operations), should be executed asynchronously without blocking the thread that called the callback. Otherwise, you can get deadlocks.
If local listener are annotated with IgniteAsyncCallback then it is executed in an async callback pool
(see IgniteConfiguration.getAsyncCallbackPoolSize()) that allow to perform a cache operations.
locLsnr - Local callback.this for chaining.IgniteAsyncCallback,
IgniteConfiguration.getAsyncCallbackPoolSize(),
ContinuousQueryWithTransformer.setLocalListener(EventListener)public javax.cache.event.CacheEntryUpdatedListener<K,V> getLocalListener()
@Deprecated public ContinuousQuery<K,V> setRemoteFilter(CacheEntryEventSerializableFilter<K,V> rmtFilter)
AbstractContinuousQuery.setRemoteFilterFactory(Factory) instead.WARNING: all operations that involve any kind of JVM-local or distributed locking (e.g., synchronization or transactional cache operations), should be executed asynchronously without blocking the thread that called the filter. Otherwise, you can get deadlocks.
If remote filter are annotated with IgniteAsyncCallback then it is executed in async callback
pool (see IgniteConfiguration.getAsyncCallbackPoolSize()) that allow to perform a cache operations.
rmtFilter - Key-value filter.this for chaining.IgniteAsyncCallback,
IgniteConfiguration.getAsyncCallbackPoolSize()public CacheEntryEventSerializableFilter<K,V> getRemoteFilter()
public ContinuousQuery<K,V> setTimeInterval(long timeInterval)
When a cache update happens, entry is first put into a buffer. Entries from buffer will
be sent to the master node only if the buffer is full (its size can be provided via Query.setPageSize(int)
method) or time provided via this method is exceeded.
Default time interval is 0 which means that
time check is disabled and entries will be sent only when buffer is full.
setTimeInterval in class AbstractContinuousQuery<K,V>timeInterval - Time interval.this for chaining.public ContinuousQuery<K,V> setAutoUnsubscribe(boolean autoUnsubscribe)
This flag indicates that query filters on remote nodes should be
automatically unregistered if master node (node that initiated the query) leaves topology. If this flag is
false, filters will be unregistered only when the query is cancelled from master node, and won't ever be
unregistered if master node leaves grid.
Default value for this flag is true.
setAutoUnsubscribe in class AbstractContinuousQuery<K,V>autoUnsubscribe - Automatic unsubscription flag.this for chaining.public ContinuousQuery<K,V> setPageSize(int pageSize)
0, then default is used.setPageSize in class Query<javax.cache.Cache.Entry<K,V>>pageSize - Optional page size.this for chaining.public ContinuousQuery<K,V> setLocal(boolean loc)
AbstractContinuousQuery.setRemoteFilterFactory(Factory) to register cache event listeners
on all cache nodes, if delivery guarantee is required.
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Ignite Database and Caching Platform : ver. 2.16.0 Release Date : December 15 2023