mongodb中sum总结

当对数据进行sum时,如果要sum字段是NumberLong型或者Integer类型  直接聚合函数就可以搞定

db.getCollection('aUAUserCurrencyDetails').aggregate(
            [
                {
                    $match : {  "memberId":321318604292097 , "issuedStatus":1  }
                } ,
               
              
                {
                    $group :
                        {
                            _id : "$memberId", totalAmount: {$sum:"$shouldCurrencyNums"},count: { $sum: 1 }
                        }
                }
                ,{$sort:{count:-1}}
            ]
        )

注: 其中 aUAUserCurrencyDetails 是表名,match中的memberId和issuedStatus是过滤的条件,group是分组查询的条件,shouldCurrencyNums是我要sum的字段

​

对应Java的写法:

Aggregation agg = Aggregation.newAggregation(
                Aggregation.match(Criteria.where("memberId").is(memberId).and("issuedStatus").is(1))
                , Aggregation.group("memberId").sum("shouldCurrencyNums").as("totalAmount"),
                Aggregation.sort(Sort.Direction.DESC, "totalAmount")
        );
        AggregationResults results = mongoTemplate.aggregate(agg, "aUAUserCurrencyDetails", BasicDBObject.class);
        //得到结果
        List basicDBObjectList = results.getMappedResults();
        if (!PubMethod.isEmpty(basicDBObjectList)) {
            for (int i = 0; i < basicDBObjectList.size(); i++) {
                        System.out.print(basicDBObjectList.get(i).get("totalAmount"));
                branchRecordMap.put("totalAmount",basicDBObjectList.get(i).get("totalAmount"));
            }
        }

但如果MongoDB中要sum的字段是String 类型(在Java中可能是BigDecimal)时,  上面的方式统计时一直是0,可以用MapReduce的方式,对应Java写法:

double total = 0L;
        Criteria criteria = new Criteria();
        criteria.and("memberId").is(memberId).and("issuedStatus").is(1);

        String reduce = "function(doc, aggr){" +
                "            aggr.total += parseFloat((Math.round((doc.shouldCurrencyNums)*100)/100).toFixed(2));" +
                "       }";
        Query query = new Query();
        if (criteria != null) {
            query.addCriteria(criteria);
        }
        DBObject result = mongoTemplate.getCollection("aUAUserCurrencyDetails").group(null,
                query.getQueryObject(),
                new BasicDBObject("total", total),
                reduce);

        Map map = result.toMap();
        if (map.size() > 0) {
            BasicDBObject bdbo = map.get("0");
            if (bdbo != null && bdbo.get("total") != null) {
                total = bdbo.getDouble("total");
            }
        }
        branchRecordMap.put("totalAmount", total);