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如何在mongoDB中使用morphia获取累加器结果？

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我在Java中使用Morphia和MongoDB，我喜欢在聚合查询中获得许多记录：

AggregationPipeline pipCount = ds.createAggregation(MyTable.class)
            .match(query1)
            .match(query2)
            .unwind("transactions")
            .match(query3)
            .group("_id", grouping("_id"), grouping("count", new Accumulator("$sum", 1)));
Iterator<MyTable> result = pipCount.aggregate(MyTable.class);

我需要使用分组（“_ id”）删除重复的结果，然后计算结果，但找不到任何方法来读取总和值...任何想法？

样本数据：

{
    "_id": "00000222",
    "create_date": ISODate("2015-05-06T07:20:31.000+0000"),
    "update_date": ISODate("2015-05-06T07:20:31.000+0000"),
    "payment": 70.0,
    "fee": 0.0,
    "type": "RECURRING",
    "currency": "USD",
    "status": "OK",
    "transactions": [{
        "_id": "111111223",
        "amount": 1260.0,
        "fee_type": "VARIABLE_ADD",
        "fee_rate": 2.75,
        "status": "ERROR",
        "charges": [{
            "_id": "2222223344",
            "amount": 1000.0,
            "recurring": true,
            "firstTime": false,
            "oneTime": true,
        }, {
            "_id": "222222222233221",
            "amount": 70.0,
            "recurring": true,
            "firstTime": true,
            "oneTime": true,
        }]
    }],
    "users": {
        "_id": "33333333332212",
        "update_date": ISODate("2015-12-18T08:03:35.000+0000"),
        "user_id": "sdjfhsd@skjksdf.com",
        "first_name": "dsjfj",
        "last_name": "skdfjf",
    }
}

结果：1

java mongodb morphia

1 回答

  • 1

    你可以尝试这样的事情 . 您不需要额外的分组 . 第一组将计算重复数，同时计算总和并计算计数并将响应映射到文档并读取计数 .

    import org.bson.Document; 

AggregationPipeline pipCount = datastore.createAggregation(MyTable.class)
            .match(query1)
            .match(query2)
            .unwind("somethingID")
            .match(query3)
            .group("_id", grouping("count", new Accumulator("$sum", 1)))
            .project(Projection.projection("count"));

    Iterator<Document> result = pipCount.aggregate(Document.class);

    while (result.hasNext()) {
        Document document = result.next();
        Integer count = document.getInteger("count");
    }
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