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java - 如何使用 HazelcastJsonValue 聚合？

问题描述

如何使用聚合HazelcastJsonValue？

我正在尝试使用：

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

但是在这两种情况下我都得到 0，而实际结果应该是 4。

这是一个示例代码：

    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);

标签： javahazelcasthazelcast-aggregate

解决方案

谓词在我看来格式不正确——在第一个中，您使用“等于”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。

对我有用的是：

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();

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