我试着运行一个$graphLookup类似于下面的打印演示：

目标是，给定一个特定的记录（注释$match），通过immediateAncestors属性检索它的完整“路径”。如你所见，它没有发生。
我在这里介绍了$convert来处理collection中的_id作为string，相信可以与_id记录列表中的immediateAncestors进行“匹配”（这是一个string）。
所以，我用不同的数据进行了另一个测试（没有涉及到ObjectIds）：

db.nodos.insert({"id":5,"name":"cinco","children":[{"id":4}]})
db.nodos.insert({"id":4,"name":"quatro","ancestors":[{"id":5}],"children":[{"id":3}]})
db.nodos.insert({"id":6,"name":"seis","children":[{"id":3}]})
db.nodos.insert({"id":1,"name":"um","children":[{"id":2}]})
db.nodos.insert({"id":2,"name":"dois","ancestors":[{"id":1}],"children":[{"id":3}]})
db.nodos.insert({"id":3,"name":"três","ancestors":[{"id":2},{"id":4},{"id":6}]})
db.nodos.insert({"id":7,"name":"sete","children":[{"id":5}]})

db.nodos.aggregate( [
  { $match: { "id": 3 } },
  { $graphLookup: {
      from: "nodos",
      startWith: "$ancestors.id",
      connectFromField: "ancestors.id",
      connectToField: "id",
      as: "ANCESTORS_FROM_BEGINNING"
    }
  },
  { $project: {
      "name": 1,
      "id": 1,
      "ANCESTORS_FROM_BEGINNING": "$ANCESTORS_FROM_BEGINNING.id"
    }
  }
] )

{
    "_id" : ObjectId("5afe270fb4719112b613f1b4"),
    "id" : 3.0,
    "name" : "três",
    "ANCESTORS_FROM_BEGINNING" : [ 
        1.0, 
        4.0, 
        6.0, 
        5.0, 
        2.0
    ]
}

最佳答案

您目前正在使用MongoDB的开发版本，该版本具有一些功能，这些功能预计将作为官方版本随MongoDB 4.0一起发布。请注意，在最终版本发布之前，某些功能可能会发生更改，因此生产代码在提交之前应该知道这一点。
为什么$convert在这里失败
解释这一点的最好方法可能是查看更改后的示例，但将其替换为ObjectId的_id值和数组下的“strings”：

{
  "_id" : ObjectId("5afe5763419503c46544e272"),
   "name" : "cinco",
   "children" : [ { "_id" : "5afe5763419503c46544e273" } ]
},
{
  "_id" : ObjectId("5afe5763419503c46544e273"),
  "name" : "quatro",
  "ancestors" : [ { "_id" : "5afe5763419503c46544e272" } ],
  "children" : [ { "_id" : "5afe5763419503c46544e277" } ]
},
{ 
  "_id" : ObjectId("5afe5763419503c46544e274"),
  "name" : "seis",
  "children" : [ { "_id" : "5afe5763419503c46544e277" } ]
},
{ 
  "_id" : ObjectId("5afe5763419503c46544e275"),
  "name" : "um",
  "children" : [ { "_id" : "5afe5763419503c46544e276" } ]
}
{
  "_id" : ObjectId("5afe5763419503c46544e276"),
  "name" : "dois",
  "ancestors" : [ { "_id" : "5afe5763419503c46544e275" } ],
  "children" : [ { "_id" : "5afe5763419503c46544e277" } ]
},
{ 
  "_id" : ObjectId("5afe5763419503c46544e277"),
  "name" : "três",
  "ancestors" : [
    { "_id" : "5afe5763419503c46544e273" },
    { "_id" : "5afe5763419503c46544e274" },
    { "_id" : "5afe5763419503c46544e276" }
  ]
},
{ 
  "_id" : ObjectId("5afe5764419503c46544e278"),
  "name" : "sete",
  "children" : [ { "_id" : "5afe5763419503c46544e272" } ]
}

db.strcoll.aggregate([
  { "$match": { "name": "três" } },
  { "$addFields": {
    "_id": { "$toString": "$_id" }
  }},
  { "$graphLookup": {
    "from": "strcoll",
    "startWith": "$ancestors._id",
    "connectFromField": "ancestors._id",
    "connectToField": "_id",
    "as": "ANCESTORS_FROM_BEGINNING"
  }},
  { "$project": {
    "name": 1,
    "ANCESTORS_FROM_BEGINNING": "$ANCESTORS_FROM_BEGINNING._id"
  }}
])

{
        "_id" : "5afe5763419503c46544e277",
        "name" : "três",
        "ANCESTORS_FROM_BEGINNING" : [ ]
}

db.createView("idview","strcoll",[
  { "$addFields": {
    "ancestors": {
      "$ifNull": [ 
        { "$map": {
          "input": "$ancestors",
          "in": { "_id": { "$toObjectId": "$$this._id" } }
        }},
        "$$REMOVE"
      ]
    },
    "children": {
      "$ifNull": [
        { "$map": {
          "input": "$children",
          "in": { "_id": { "$toObjectId": "$$this._id" } }
        }},
        "$$REMOVE"
      ]
    }
  }}
])

db.idview.aggregate([
  { "$match": { "name": "três" } },
  { "$graphLookup": {
    "from": "idview",
    "startWith": "$ancestors._id",
    "connectFromField": "ancestors._id",
    "connectToField": "_id",
    "as": "ANCESTORS_FROM_BEGINNING"
  }},
  { "$project": {
    "name": 1,
    "ANCESTORS_FROM_BEGINNING": "$ANCESTORS_FROM_BEGINNING._id"
  }}
])

{
    "_id" : ObjectId("5afe5763419503c46544e277"),
    "name" : "três",
    "ANCESTORS_FROM_BEGINNING" : [
        ObjectId("5afe5763419503c46544e275"),
        ObjectId("5afe5763419503c46544e273"),
        ObjectId("5afe5763419503c46544e274"),
        ObjectId("5afe5763419503c46544e276"),
        ObjectId("5afe5763419503c46544e272")
    ]
}

db.strcoll.aggregate([
  { "$addFields": {
    "ancestors": {
      "$ifNull": [ 
        { "$map": {
          "input": "$ancestors",
          "in": { "_id": { "$toObjectId": "$$this._id" } }
        }},
        "$$REMOVE"
      ]
    },
    "children": {
      "$ifNull": [
        { "$map": {
          "input": "$children",
          "in": { "_id": { "$toObjectId": "$$this._id" } }
        }},
        "$$REMOVE"
      ]
    }
  }}
  { "$out": "fixedcol" }
])

var updates = [];

db.strcoll.find().forEach(doc => {
  var update = { '$set': {} };

  if ( doc.hasOwnProperty('children') )
    update.$set.children = doc.children.map(e => ({ _id: new ObjectId(e._id) }));
  if ( doc.hasOwnProperty('ancestors') )
    update.$set.ancestors = doc.ancestors.map(e => ({ _id: new ObjectId(e._id) }));

  updates.push({
    "updateOne": {
      "filter": { "_id": doc._id },
      update
    }
  });

  if ( updates.length > 1000 ) {
    db.strcoll.bulkWrite(updates);
    updates = [];
  }

})

if ( updates.length > 0 ) {
  db.strcoll.bulkWrite(updates);
  updates = [];
}

const { MongoClient, ObjectID: ObjectId } = require('mongodb');
const EJSON = require('mongodb-extended-json');

const uri = 'mongodb://localhost/';

const log = data => console.log(EJSON.stringify(data, undefined, 2));

(async function() {

  try {

    const client = await MongoClient.connect(uri);
    let db = client.db('test');
    let coll = db.collection('strcoll');

    let fields = ["ancestors", "children"];

    let cursor = coll.find({
      $or: fields.map(f => ({ [`${f}._id`]: { "$type": "string" } }))
    }).project(fields.reduce((o,f) => ({ ...o, [f]: 1 }),{}));

    let batch = [];

    for await ( let { _id, ...doc } of cursor ) {

      let $set = {};
      let arrayFilters = [];

      for ( const f of fields ) {
        if ( doc.hasOwnProperty(f) ) {
          $set = { ...$set,
            ...doc[f].reduce((o,{ _id },i) =>
              ({ ...o, [`${f}.$[${f.substr(0,1)}${i}]._id`]: ObjectId(_id) }),
              {})
          };

          arrayFilters = [ ...arrayFilters,
            ...doc[f].map(({ _id },i) =>
              ({ [`${f.substr(0,1)}${i}._id`]: _id }))
          ];
        }
      }

      if (arrayFilters.length > 0)
        batch = [ ...batch,
          { updateOne: { filter: { _id }, update: { $set }, arrayFilters } }
        ];

      if ( batch.length > 1000 ) {
        let result = await coll.bulkWrite(batch);
        batch = [];
      }

    }

    if ( batch.length > 0 ) {
      log({ batch });
      let result = await coll.bulkWrite(batch);
      log({ result });
    }

    await client.close();

  } catch(e) {
    console.error(e)
  } finally {
    process.exit()
  }

})()

{
  "updateOne": {
    "filter": {
      "_id": {
        "$oid": "5afe5763419503c46544e272"
      }
    },
    "update": {
      "$set": {
        "children.$[c0]._id": {
          "$oid": "5afe5763419503c46544e273"
        }
      }
    },
    "arrayFilters": [
      {
        "c0._id": "5afe5763419503c46544e273"
      }
    ]
  }
},
{
  "updateOne": {
    "filter": {
      "_id": {
        "$oid": "5afe5763419503c46544e273"
      }
    },
    "update": {
      "$set": {
        "ancestors.$[a0]._id": {
          "$oid": "5afe5763419503c46544e272"
        },
        "children.$[c0]._id": {
          "$oid": "5afe5763419503c46544e277"
        }
      }
    },
    "arrayFilters": [
      {
        "a0._id": "5afe5763419503c46544e272"
      },
      {
        "c0._id": "5afe5763419503c46544e277"
      }
    ]
  }
},
{
  "updateOne": {
    "filter": {
      "_id": {
        "$oid": "5afe5763419503c46544e274"
      }
    },
    "update": {
      "$set": {
        "children.$[c0]._id": {
          "$oid": "5afe5763419503c46544e277"
        }
      }
    },
    "arrayFilters": [
      {
        "c0._id": "5afe5763419503c46544e277"
      }
    ]
  }
},
{
  "updateOne": {
    "filter": {
      "_id": {
        "$oid": "5afe5763419503c46544e275"
      }
    },
    "update": {
      "$set": {
        "children.$[c0]._id": {
          "$oid": "5afe5763419503c46544e276"
        }
      }
    },
    "arrayFilters": [
      {
        "c0._id": "5afe5763419503c46544e276"
      }
    ]
  }
},
{
  "updateOne": {
    "filter": {
      "_id": {
        "$oid": "5afe5763419503c46544e276"
      }
    },
    "update": {
      "$set": {
        "ancestors.$[a0]._id": {
          "$oid": "5afe5763419503c46544e275"
        },
        "children.$[c0]._id": {
          "$oid": "5afe5763419503c46544e277"
        }
      }
    },
    "arrayFilters": [
      {
        "a0._id": "5afe5763419503c46544e275"
      },
      {
        "c0._id": "5afe5763419503c46544e277"
      }
    ]
  }
},
{
  "updateOne": {
    "filter": {
      "_id": {
        "$oid": "5afe5763419503c46544e277"
      }
    },
    "update": {
      "$set": {
        "ancestors.$[a0]._id": {
          "$oid": "5afe5763419503c46544e273"
        },
        "ancestors.$[a1]._id": {
          "$oid": "5afe5763419503c46544e274"
        },
        "ancestors.$[a2]._id": {
          "$oid": "5afe5763419503c46544e276"
        }
      }
    },
    "arrayFilters": [
      {
        "a0._id": "5afe5763419503c46544e273"
      },
      {
        "a1._id": "5afe5763419503c46544e274"
      },
      {
        "a2._id": "5afe5763419503c46544e276"
      }
    ]
  }
},
{
  "updateOne": {
    "filter": {
      "_id": {
        "$oid": "5afe5764419503c46544e278"
      }
    },
    "update": {
      "$set": {
        "children.$[c0]._id": {
          "$oid": "5afe5763419503c46544e272"
        }
      }
    },
    "arrayFilters": [
      {
        "c0._id": "5afe5763419503c46544e272"
      }
    ]
  }
}

关于mongodb - 将ObjectId与$ graphLookup的字符串匹配，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/50402500/