如何使用mongoDB中的morphia獲取累加器結果？

Question

我在Java中使用嗎啡與MongoDB中，我想獲得多項紀錄聚集查詢這樣的：

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); 

我需要使用分組（「_ ID」），刪除重複的結果，然後算結果，但無法找到任何方式來讀取總和值... 任何想法？

樣本數據：

{ 
    "_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", 
    } 
} 

結果：1

Answer 1

你可以嘗試這樣的事情。你不需要額外的分組。第一組將處理重複數據，並計算總數並計算計數並將響應映射到文檔並讀取計數。

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"); 
    }