How tree structure with mongodb? - node.js

Question

Hello I need to know if it is possible to generate a structure tree so that you understand me I have this model:
const StructureSchema = new Schema({
parent: { type: Schema.ObjectId, ref: 'article' },
child : { type: Schema.ObjectId, ref: 'article' },
quantity: { type: Number, default: 0 },
utilization : { type: String},
increasePrice : { type : Number},
optional : { type : Boolean, default : false}
});
It happens that even there it returns me correct when it is a single level it happens that Child can act as Parent too and I would like to bring that structure too.
I was watching $ graphLookup but I could not implement it as I want some idea how to achieve it?

Answer 1

You seem to be using ObjectId (i.e. other _id) for the parent and child keys. I would recommend simplifying your design to using just parent as follows:
var r =
[
{"_id":0, otherData:"foo2"}
,{"_id":3, parent:0, otherData:"foo1"}
,{"_id":4, parent:0, otherData:"foo2"}
,{"_id":5, parent:0, otherData:"foo2"}
,{"_id":6, parent:0, otherData:"foo3"}
,{"_id":7, parent:6, otherData:"foo3"}
,{"_id":8, parent:6, otherData:"foo3"}
,{"_id":9, parent:8, otherData:"foo3"}
];
In this design a record without a parent is the "root."
Both parent-to-child and child-to-parent lookups are possible.
// Child-to-parent lookup:
db.foo.aggregate([
// Find the child we seek:
{$match: {_id: 9}}
// Now get the parent chain:
,{$graphLookup: {
from: "foo",
connectToField: "_id",
connectFromField: "parent",
startWith: "$parent", // usually value of connectFromField
depthField: "n",
as: "zz"
}}
]);
{
"_id" : 9,
"parent" : 8,
"otherData" : "foo3",
"zz" : [
{
"_id" : 8,
"parent" : 6,
"otherData" : "foo3",
"n" : NumberLong(0)
},
{
"_id" : 0,
"otherData" : "foo2",
"n" : NumberLong(2)
},
{
"_id" : 6,
"parent" : 0,
"otherData" : "foo3",
"n" : NumberLong(1)
}
]
}
// Parent-to-child lookup:
db.foo.aggregate([
// Find the parent we seek:
{$match: {_id: 0}} // just go for the top for fun
// Now get the child chains; there can be >1 child for a parent:
,{$graphLookup: {
from: "foo",
connectToField: "parent",
connectFromField: "_id",
startWith: "$_id", // usually value of connectFromField
depthField: "n",
as: "zz"
}}
]);
{
"_id" : 0,
"otherData" : "foo2",
"zz" : [
{
"_id" : 5,
"parent" : 0,
"otherData" : "foo2",
"n" : NumberLong(0)
},
{
"_id" : 8,
"parent" : 6,
"otherData" : "foo3",
"n" : NumberLong(1)
},
{
"_id" : 6,
"parent" : 0,
"otherData" : "foo3",
"n" : NumberLong(0)
},
{
"_id" : 9,
"parent" : 8,
"otherData" : "foo3",
"n" : NumberLong(2)
},
{
"_id" : 4,
"parent" : 0,
"otherData" : "foo2",
"n" : NumberLong(0)
},
{
"_id" : 3,
"parent" : 0,
"otherData" : "foo1",
"n" : NumberLong(0)
},
{
"_id" : 7,
"parent" : 6,
"otherData" : "foo3",
"n" : NumberLong(1)
}
]
}