MongoDB get all descendants-CodePudding

I am building an application to show tree structures via jstree. The data is stored in flat array format like the following.

{id:1,text:"Parent",xpath:"/Parent",parent:"#",children:true}

{id:2,text:"Child1",xpath:"/Parent/Child1",parent:1,children:false}

{id:3,text:"Child2",xpath:"/Parent/Child2",parent:1,children:true}

{id:4,text:"Child3",xpath:"/Parent/Child3",parent:1,children:false}

{id:5,text:"Grandchild1",xpath:"/Parent/Child2/Grandchild1",parent:3,children:false}

{id:6,text:"Grandchild2",xpath:"/Parent/Child2/Grandchild2",parent:3,children:false}

{id:7,text:"Grandchild3",xpath:"/Parent/Child2/Grandchild3",parent:3,children:false}

Every document contains a node and has the following attributes

id -> Uniquer identifier

text -> node name

xpath -> path from root to node

parent -> node id of node's parent

children -> Boolean value representing whether the node has children

Once I provide a particular node id. I want all the descendants of the node. For example, if I provide node id as 1, I need results in the following pattern.

{
1:[{id:2,...},{id:3,...},{id:4,...}],
3:[{id:5,...},{id:6,...},{id:7,...}]
}

Is there any way to achieve this? Should I change the format in which data is stored to achieve this? Open to any suggestion. Thanks!

CodePudding user response：

I'm not sure how flexible you are with the output format, but here's one way to output all the descending generations of a given "id".

db.collection.aggregate([
  {"$match": {"id": 1}},
  {
    "$graphLookup": {
      "from": "collection",
      "startWith": "$id",
      "connectFromField": "id",
      "connectToField": "parent",
      "as": "descendents",
      "depthField": "generation"
    }
  },
  {"$unwind": "$descendents"},
  {"$sort": {"descendents.id": 1}},
  {
    "$group": {
      "_id": "$descendents.generation",
      "theChildren": {"$push": "$descendents"}
    }
  },
  {
    "$project": {
      "_id": 0,
      "theChildren": 1,
      "generation": {"$toInt": "$_id"},
      "parent": {"$first": "$theChildren.parent"}
    }
  }
])

Try it on mongoplayground.net.