MongoDB: $filter multiple arrays - mongodb

Question

I have an collection like:
{
_id: 0,
items: [
{ item_id: 43, quantity: 2, price: 10 },
{ item_id: 2, quantity: 1, price: 240 }
],
T: [
{ item_id: 2993, quantity: 3, price: 110 },
{ item_id: 90103, quantity: 4, price: 5 },
{ item_id: 398, quantity: 1, price: 300 }
]
}
{
_id: 1,
items: [
{ item_id: 23, quantity: 3, price: 110 },
{ item_id: 103, quantity: 4, price: 5 },
{ item_id: 38, quantity: 1, price: 300 }
],
T: [
{ item_id: 23, quantity: 3, price: 110 },
{ item_id: 103, quantity: 4, price: 5 },
{ item_id: 38, quantity: 1, price: 300 }
]
}
{
_id: 2,
items: [
{ item_id: 4, quantity: 1, price: 23 }
],
T: [
{ item_id: 203, quantity: 3, price: 110 },
{ item_id: 003, quantity: 4, price: 5 },
{ item_id: 398, quantity: 1, price: 300 }
]
}
I want to return a all the items in the items array with a price >= 100. That is done with the following:
$project: {
items: {
$filter: {
input: "$items",
as: "item",
cond: { $gte: [ "$$item.price", 100 ] }
}
}
}
How can I expand this expression to $filter on the items array and the T array all elements that have a price >= 100?

Answer 1

You can include both the items and T fields in the same $project, each with its own $filter:
db.test.aggregate([
{$project: {
items: {
$filter: {
input: "$items",
as: "item",
cond: { $gte: [ "$$item.price", 100 ] }
}
},
T: {
$filter: {
input: "$T",
as: "t",
cond: { $gte: [ "$$t.price", 100 ] }
}
}
}}
])