MongoDB使用聚合框架计算字段为true的次数

Question

简介

尝试计算字段为"seed"的用户等于"false"的次数

(邮件(收集示例

{
 to : "jimmy",
 from : "johny",
 message : "Hey",
 seen: false
},
{
 to : "jimmy",
 from : "Maggy",
 message : "Hello",
 seen: true
},
{
 to : "jimmy",
 from : "Sam",
 message : "How are you?",
 seen: false
},
{
 to : "jimmy",
 from : "johny",
 message : "It's me again",
 seen: false
}

Java方法w/Mongo聚合

  //WHERE 'to' EQUALS 'jimmmy'
  //COUNT 'seen' EQUALS 'false'

我尝试过的

    public int getTotalUnseen(String toUser){
AggregateIterable<Document> iterable = db.getCollection("mail").aggregate(asList(
        new Document("$match", new Document("to", "jimmy")),
        new Document("$group", new Document("_id", "$seen").append("count", new Document("$sum", 1)))));
    }

期望结果

int x = getTotalUnseenCount("jimmy");
System.out.println("Result : "+ x);

//Result : 3

Answer 1

您可以尝试以下操作：

Query query = new Query();
query.addCriteria(Criteria.where("to").is("jimmy").and("seen").is(true));    
mongoTemplate.count(query, "mail");