如何在HazelcastJsonValue中使用聚合？

Question

如何在HazelcastJsonValue中使用聚合

我试着使用：

Long count = map1.aggregate(Aggregators.count(), e -> "name='John'".equals(e.getValue()));        
Long count = map1.aggregate(Aggregators.count("name='John'"));

但我在两种情况下都得到了0，而实际结果应该是4。

下面是一个示例代码：

    HazelcastInstance hazelCast = Hazelcast.newHazelcastInstance();
    IMap<String, HazelcastJsonValue> map1 = hazelCast.getMap("map1");

    map1.put("1", new HazelcastJsonValue("{"name":"John", "age":31, "city":"New York"}"));
    map1.put("2",  new HazelcastJsonValue("{"name":"John", "age":31, "city":"New York"}"));
    map1.put("3", new HazelcastJsonValue("{"name":"John", "age":31, "city":"New York"}"));
    map1.put("4",  new HazelcastJsonValue("{"name":"John", "age":31, "city":"New York"}"));
    
    Long count = map1.aggregate(Aggregators.count(), e -> "name='John'".equals(e.getValue()));
    Long count = map1.aggregate(Aggregators.count("name='John'"));

    System.out.println(count);

Answer 1

在我看来，谓词的格式不是很好--在第一个谓词中，您使用'equals‘将整个JSON文档(多个字段)与文档的一部分进行比较，因此它永远不会匹配。

对我来说起作用的是：

Config c = new Config();
HazelcastInstance hazelCast = Hazelcast.newHazelcastInstance(c);
IMap<String, HazelcastJsonValue> map1 = hazelCast.getMap("map1");

HazelcastJsonValue jsv = new HazelcastJsonValue("{\"name\":\"John\", \"age\":31, \"city\":\"New York\"}");
map1.put("A", jsv);
map1.put("B", jsv);

Predicate p = Predicates.equal("name", "John");
long count = map1.aggregate(Aggregators.count(), p);
System.out.println("Count: " + count);
hazelCast.shutdown();