How to select two-level data structure in MongoDB? - mongodb

Question

I'm developing an online shopping application, which has two-level product type. Now I'm using MongoDB to store it. My programming language is TypeScript.
My model is like below:
class ProductTypeModel {
_id: ObjectID;
name: string;
sort: number; // sort
status: number; // enable | disable
children: Object[]; // sub types, like [{ _id: ObjectID('xx', name: 'xx', sort: xx, status: xx) }]
create_time: Date;
update_time: Date;
}
If we have data like below:
{
"_id" : ObjectId("5b8fe56218de48345a6b7079"),
"create_time" : ISODate("2018-09-05T14:17:06.912Z"),
"update_time" : ISODate("2018-09-05T14:17:06.912Z"),
"name" : "Books",
"sort" : 0,
"status" : 1,
"children" : [
{
"_id" : ObjectId("5b8fe56218de48345a6b7075"),
"name" : "Computer",
"sort" : 1,
"status" : 1
},
{
"_id" : ObjectId("5b8fe56218de48345a6b7076"),
"name" : "Math",
"sort" : 2,
"status" : 0
},
{
"_id" : ObjectId("5b8fe56218de48345a6b7077"),
"name" : "Novel",
"sort" : 3,
"status" : 1
}
]
}
How can I select types and children types with status=1 ?
My current solution is to select base types first, and traverse to exclude children whose status is 0. Is there a better way to do it?

Answer 1

$redact aggregation stage this will do the job:
db['03'].aggregate(
[
{
$redact: {
$cond: {
if: { $eq: [ "$status", 1 ] },
then: "$$DESCEND",
else: "$$PRUNE"
}
}
},
],
);
output :
{
"_id" : ObjectId("5b8fe56218de48345a6b7079"),
"create_time" : ISODate("2018-09-05T16:17:06.912+0200"),
"update_time" : ISODate("2018-09-05T16:17:06.912+0200"),
"name" : "Books",
"sort" : NumberInt(0),
"status" : NumberInt(1),
"children" : [
{
"_id" : ObjectId("5b8fe56218de48345a6b7075"),
"name" : "Computer",
"sort" : NumberInt(1),
"status" : NumberInt(1)
},
{
"_id" : ObjectId("5b8fe56218de48345a6b7077"),
"name" : "Novel",
"sort" : NumberInt(3),
"status" : NumberInt(1)
}
]
}