Question

这是我的Mongo DB聚合查询： db.EmployeeResults.aggregate（[

    {
        $match: { 
            "_id.employeeID" : "e2c42da3-1bfa-49fe-9a3d-6528af45c54d",
            "Versions.scope" : "INPUT_QUALITY"

        }
    },
{       
    $project: {
        Versions: 1,
        MaxVersion: { $max: "$Versions.version" }
    }
},
{
    $project: {
        Versions: {
            $filter: {
                input: "$Versions",
                as: "x",
                cond: { $eq: [ "$$x.version", "$MaxVersion" ] }
            }
        }
    }
},
{
    $unwind: "$Versions"
}

]）

上面的Java查询写为：

AggregationOutput agg1 = db.getCollection("EmployeeResults").aggregate(
        new BasicDBObject().append("$match",
                new BasicDBObject().append("_id.employeeID", "e2c42da3-1bfa-49fe-9a3d-6528af45c54d").append("Versions.scope","INPUT_QUALITY")),
        new BasicDBObject().append(
                "$project",
                new BasicDBObject().append("Versions", 1).append("MaxVersion",
                        new BasicDBObject().append("$max", "$Versions.version"))),
        new BasicDBObject().append(
                "$project",
                 new BasicDBObject().append("Versions",new BasicDBObject().append("$filter", new BasicDBObject().append("input", "$Versions").append("cond", new BasicDBObject().append("$eq", Arrays.asList("$$this.version", "$MaxVersion")))))),
        new BasicDBObject().append("$unwind", "$Versions"),
        new BasicDBObject().append(
                "$project",
                new BasicDBObject().append("errors", "$Versions.errors")
        )
                );

我试图将Java中的同一聚合查询转换为Groovy ：（基本上将所有与mongo相关的表达式替换为单引号“ $ project”-'$ project'）

    AggregationOutput agg1 = db.getCollection("EmployeeResults").aggregate(
            new BasicDBObject().append('$match',
                    new BasicDBObject().append("_id.employeeID", "e2c42da3-1bfa-49fe-9a3d-6528af45c54d").append("Versions.scope", "INPUT_QUALITY")),
            new BasicDBObject().append('$project',
                    new BasicDBObject().append("Versions", 1).append("MaxVersion", new BasicDBObject().append('$max', '$versions.version'))),
            new BasicDBObject().append('$project',
                    new BasicDBObject().append("Versions", new BasicDBObject().append('$filter', new BasicDBObject().append("input", '$Versions').append("cond", new BasicDBObject().append('$eq', asList('$$this.version', '$MaxVersion')))))),
            new BasicDBObject().append('$unwind', '$Versions'),
            new BasicDBObject().append('$project',
                    new BasicDBObject().append("errors", '$Versions.errors'))
    )

我得到零行，因为在$ filter“ cond”中找不到正确的内容，无法在$$ this.version中找到MaxVersion。我的Java程序返回18行，但是上面的常规代码给了我0行。当我尝试在Groovy程序中注释查询的最后2行时，它向我返回行很感谢任何形式的帮助。预先感谢。

groovy中的MongoDB聚合返回0行，而Java中的MongoDB聚合返回许多行

0 个答案: