Question

＆＃39; setInitialQuery＆＃39;？

的目的是什么？

IgniteCache<Integer, String> cache = ignite.cache("mycache");

// Create new continuous query.
ContinuousQuery<Integer, String> qry = new ContinuousQuery<>();

// Optional initial query to select all keys greater than 10.
qry.setInitialQuery(new ScanQuery<Integer, String>((k, v) -> k > 10)):

// Callback that is called locally when update notifications are received.
qry.setLocalListener((evts) -> 
    evts.forEach(e -> System.out.println("key=" + e.getKey() + ", val=" + e.getValue())));

// This filter will be evaluated remotely on all nodes.
// Entry that pass this filter will be sent to the caller.
qry.setRemoteFilter(e -> e.getKey() > 10);

// Execute query.
try (QueryCursor<Cache.Entry<Integer, String>> cur = cache.query(qry)) {
  // Iterate through existing data stored in cache.
  for (Cache.Entry<Integer, String> e : cur)
    System.out.println("key=" + e.getKey() + ", val=" + e.getValue());

  // Add a few more keys and watch a few more query notifications.
  for (int i = 5; i < 15; i++)
    cache.put(i, Integer.toString(i));
}

以上代码无需设置初始查询即可运行。试着了解什么时候会使用＆＃39; setInitialQuery＆＃39;。

Answer 1

初始查询允许在开始侦听更新之前将光标放在缓存中已有的数据上。它确实是可选的。

Apache Ignite - 连续查询

1 个答案: