mongodb lookup as array.array code example
Example 1: lookup in mongodb array
> db.demo396.aggregate([
... { "$lookup": {
... "from": "demo395",
... "let": { "details": "$details" },
... "pipeline": [
... { "$match": { "$expr": { "$in": [ "$_id", "$$details" ] } } }
... ],
... "as": "output"
... }}
... ])
Example 2: mongodb find array with element
// Finds all documents that have a property named "tags"
// which has at least one array element matching "red"
db.inventory.find( { tags: "red" } )