mongodb - Mongodb: apply lookup on same collection and get sub-categories inside parent category array using a single query
问题描述
Here is the schema of category collection, where I am storing categories, sub-categories and further children of sub-categories.
mongoose.Schema({
name:{ type: Array, required: true}, //It is an array because name can be in multiple languages
path:{ type: String, required: true}, // All parent categories in an order to have immediate parent at the end
parent: { type: String, required: true}
});
I have added index over all the three fields. Now, what the requirement is - need to get all children categories nested in parent categories array returned as a result of single query.
For categories that are root, parent
has '/'
and path
is '/' separated ids upto immediate parent.
What I have tried is, getting all subcategories of a parent category by passing the _id
, Like -
categoryModel.find({parent: /^\/documentId/})
But, I want in result all the parent categories with sub categories nested in it. How to do that?
Expected output -
[
{
_id: '1',
name: 'MainCategory1',
path: '/'
parent: '/',
children: [
{
_id: '3',
name: 'SubCategory3',
parent: '1',
path: '/1'
},
]
},
{
_id: '2',
name: 'MainCategory2',
path: '/'
parent: '/',
children: [
{
_id: '5',
name: 'SubCategory5',
parent: '2',
path: '/2',
children: [
{
_id: '7',
name: 'SubCategory7',
parent: '5',
path: '/2/5',
children: [
{
_id: '9',
name: 'SubCategory7',
parent: '7',
path: '/2/5/7',
}]
},
]
},
]
},
]
解决方案
我通过使用聚合$graphlookup
和得到了结果$match
,尽管它不是所需的确切格式。我需要的格式是在得到查询响应后构建的。这是我的查询
{ $match: {parent : '/'}},
{
$graphLookup: {
from: "category",
startWith: "$_id",
connectFromField: "_id",
connectToField: "parent",
depthField: "depth",
as: "children"
},
},
这是我从上面的查询中得到的响应
[{
"_id":"1",
"name":"category1",
"parent":'/',
"children":[
{
"_id":"3",
"name":"Sub-Category1",
"parent":"1",
"depth":0
}
]
},
{
"_id":"2",
"name":"Category2",
"parent":'/',
"children":[
{
"_id":"4",
"name":"Sub-Category2",
"parent":"2",
"depth":0
},
{
"_id":"5",
"name":"Sub-Category3",
"parent":"4",
"depth":1
}
]
}]
其中depth 0,depth 1是子类别相对于父类别的级别。