java - 根据条件分组和求和

Question

我使用 mongoTemplate 查询我的 mongodb 数据库，我想在我的集合中做一些计数。我想按 id 分组并包括有条件的计数。我在 mongoshell 中使用了这个查询

db.scenarios.aggregate([
    { $match: { bid: "build_1481711758" } },
    {
        $group: {
            _id: "$bid",
            nb: { $sum: 1 },
            nbS: {
                "$sum": {
                    "$cond": [
                        { "$eq": ["$scst",  true ] },  
                        1, 0 
                    ]
                }
            },
            nbE: {
                "$sum": {
                    "$cond": [
                        { "$eq": ["$scst",  false ] },  
                        1, 0 
                    ]
                }
            }
        }
    }
])

它返回我想要的，但我不知道如何将它转换为 java mongotemplate。

请帮忙:)

Answer 1

您可以将管道简化为

db.scenarios.aggregate([
    { $match: { bid: "build_1481711758" } },
    {
        $group: {
            _id: "$bid",
            nb: { $sum: 1 },
            nbS: {
                "$sum": {
                    "$cond": [ "$scst",  1, 0 ]
                }
            },
            nbE: {
                "$sum": {
                    "$cond": [ "$scst",  0, 1 ]
                }
            }
        }
    }
])

自从 $cond 运算符计算一个 boolean 表达式以返回两个指定返回表达式之一，并且 scst 字段默认返回一个 boolean 值。

如果使用支持 $cond 的当前 Spring Data 版本 运算符通过 $project 管道，然后可以将其转换为(未测试):

import static org.springframework.data.mongodb.core.aggregation.Aggregation.*;
import static org.springframework.data.mongodb.core.aggregation.ConditionalOperators.Cond.*;
import org.springframework.data.mongodb.core.query.Criteria;

Cond operatorNbS = ConditionalOperators.when("scst").thenValueOf(1).otherwise(0);
Cond operatorNbE = ConditionalOperators.when("scst").thenValueOf(0).otherwise(1);

Aggregation agg = newAggregation(
    match(Criteria.where("bid").is("build_1481711758"),
    project("bid") 
        .and("scst")                            
        .applyCondition(operatorNbE, field("nbE"))
        .applyCondition(operatorNbS, field("nbS"))
    group("bid")
        .count().as("nb")
        .sum("nbE").as("nbS")
        .sum("nbE").as("nbE") 
);
AggregationResults<Scenarios> results = mongoTemplate.aggregate(agg, Scenarios.class); 
List<Scenarios> scenarios = results.getMappedResults();

---

如果您的 Spring Data 版本不支持此功能，解决方法是实现 AggregationOperation 接受 DBObject 的接口(interface):

public class CustomGroupOperation implements AggregationOperation {
    private DBObject operation;

    public CustomGroupOperation (DBObject operation) {
        this.operation = operation;
    }

    @Override
    public DBObject toDBObject(AggregationOperationContext context) {
        return context.getMappedObject(operation);
    }
}

然后执行 $group作为聚合管道中的 DBObject 操作，与您拥有的相同:

DBObject operation = (DBObject)new BasicDBObject(
    "$group", new BasicDBObject(
        "_id", "$bid"
    )
    .append( "nb", new BasicDBObject("$sum", 1) )
    .append(
        "nbS", new BasicDBObject(
            "$sum", new BasicDBObject(
                "$cond", new Object[]{ "$scst", 1, 0 }
            )
        )
    ).append(
        "nbE", new BasicDBObject(
            "$sum", new BasicDBObject(
                "$cond", new Object[]{ "$scst", 0, 1 }
            )
        )
    )
);

然后您可以将其用作:

Aggregation agg = newAggregation(
    match(Criteria.where("bid").is("build_1481711758"),
    new CustomGroupOperation(operation)
);

---

要获得执行速度比上述方法快得多的更灵活、性能更好的方法，请考虑如下运行替代管道

 db.scenarios.aggregate([
    { $match: { bid: "build_1481711758" } },
    { 
        "$group": {
            "_id": { 
                "bid": "$bid",
                "scst": "$scst"
            },
            "count": { "$sum": 1 }
        }
    },
    { 
        "$group": {
            "_id": "$_id.bid",
            "counts": {
                "$push": {
                    "scst": "$_id.scst",
                    "count": "$count"
                }
            }
        }
    }
])