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如何从MongoDB中递归获取数据?

mongodb javascript

Javid Asgarov · 技术社区 · 6 年前

我在MongoDB中有一些数据(我们称之为日志),比如说:

{
  name: String,
  category_id: String
}

每个类别都有 家长ID . 我想要的是尽可能地从树上获取第一个父级,并从所谓的日志中获取每个数据项的所有父级。

我首先想到的是:在控制器中获取所有项目,然后递归地获取所有父类。这可能行得通,但似乎既单调又错误。

对于模型本身,可能还有更好的事情要做,比如静态方法。

所以,我的问题是,您如何处理MongoDB?我知道有聚合,我使用过几次,但如果按某个具有特定值的字段,我可以看到如何使用它们。但是在这里,你得到一个项目,通过它的父ID获得下一个项目,等等。

1 回复 | 直到 6 年前

matthPen 6 年前

$graphLookup

#logs collection
db.logs.find({});
{ 
    "_id" : ObjectId("5b4f2970d42ef3178d108e86"), 
    "name" : "01", 
    "category" : "cat1"
}
{ 
    "_id" : ObjectId("5b4f2981d42ef3178d108e87"), 
    "name" : "02", 
    "category" : "cat1"
}
{ 
    "_id" : ObjectId("5b4f298ad42ef3178d108e88"), 
    "name" : "03", 
    "category" : "cat2"
}
{ 
    "_id" : ObjectId("5b4f2997d42ef3178d108e89"), 
    "name" : "04", 
    "category" : "cat2"
}
{ 
    "_id" : ObjectId("5b4f29bed42ef3178d108e8a"), 
    "name" : "015", 
    "category" : "cat10"
}

#categories collection
db.categories.find({});
{ 
    "_id" : "cat1", 
    "parent_id" : "cat2"
}
{ 
    "_id" : "cat2", 
    "parent_id" : "cat10"
}
{ 
    "_id" : "cat10"
}

db.logs.aggregate(
    [
        {
            $graphLookup: {
                from: "categories",
                startWith: "$category", // connectToField value(s) that recursive search starts with
                connectFromField: "parent_id",
                connectToField: "_id",
                as: "related_categories",
                maxDepth: 10, // optional
                depthField: "depthField" // optional - name of field in output documents
            }
        },
    ],
);

{ 
    "_id" : ObjectId("5b4f2970d42ef3178d108e86"), 
    "name" : "01", 
    "category" : "cat1", 
    "related_categories" : [
        {
            "_id" : "cat10", 
            "depthField" : NumberLong(2)
        }, 
        {
            "_id" : "cat2", 
            "parent_id" : "cat10", 
            "depthField" : NumberLong(1)
        }, 
        {
            "_id" : "cat1", 
            "parent_id" : "cat2", 
            "depthField" : NumberLong(0)
        }
    ]
}
{ 
    "_id" : ObjectId("5b4f2981d42ef3178d108e87"), 
    "name" : "02", 
    "category" : "cat1", 
    "related_categories" : [
        {
            "_id" : "cat10", 
            "depthField" : NumberLong(2)
        }, 
        {
            "_id" : "cat2", 
            "parent_id" : "cat10", 
            "depthField" : NumberLong(1)
        }, 
        {
            "_id" : "cat1", 
            "parent_id" : "cat2", 
            "depthField" : NumberLong(0)
        }
    ]
}
{ 
    "_id" : ObjectId("5b4f298ad42ef3178d108e88"), 
    "name" : "03", 
    "category" : "cat2", 
    "related_categories" : [
        {
            "_id" : "cat10", 
            "depthField" : NumberLong(1)
        }, 
        {
            "_id" : "cat2", 
            "parent_id" : "cat10", 
            "depthField" : NumberLong(0)
        }
    ]
}
{ 
    "_id" : ObjectId("5b4f2997d42ef3178d108e89"), 
    "name" : "04", 
    "category" : "cat2", 
    "related_categories" : [
        {
            "_id" : "cat10", 
            "depthField" : NumberLong(1)
        }, 
        {
            "_id" : "cat2", 
            "parent_id" : "cat10", 
            "depthField" : NumberLong(0)
        }
    ]
}
{ 
    "_id" : ObjectId("5b4f29bed42ef3178d108e8a"), 
    "name" : "015", 
    "category" : "cat10", 
    "related_categories" : [
        {
            "_id" : "cat10", 
            "depthField" : NumberLong(0)
        }
    ]
}