Using $lookup, aggregate and set

Working with Data
1

Hi! I need help with $lookup, aggregate and set.
I have 2 collections and I want to combine both of them. The issue is my document model
a lost of dictionaries…
Appreciate the help, Thank! Tal

The first collection

{
	"_id": {
		"AccountID": "920d145d",
		"EntityName": "ABILITIES"
	},
	"EntityName": "ABILITIES",
	"Fields": [{
		"fieldName": "ABILITYCODE",
		"SourceDataType": "Edm.String",
		"KeyFlag": true
	}, {
		"fieldName": "ABILITYDES",
		"SourceDataType": "Edm.String",
		"KeyFlag": false
	} ]
}

The second collection:

{
	"_id": {
		"$oid": "63b3eab829615d432868f67e"
	},
	"SourceSystem": "Priority",
	"SourceDataType": "Edm.String",
	"MySQLDatatype": "TINYTEXT"
},
{
	"_id": {
		"$oid": "63b3ed1e29615d432868f67f"
	},
	"SourceSystem": "Priority",
	"SourceDataType": "Edm.Int64",
	"MySQLDatatype": "BIGINT(64)"
}

I want to turn the first collection to this:

{
	"_id": {
		"AccountID": "920d145d",
		"EntityName": "ABILITIES"
	},
	"EntityName": "ABILITIES",
	"Fields": [{
		"fieldName": "ABILITYCODE",
		"SourceDataType": "Edm.Int64",
        "MySQLDatatype": "BIGINT(64)",
		"KeyFlag": true
	}, {
		"fieldName": "ABILITYDES",
		"SourceDataType": "Edm.String",
        "MySQLDatatype": "TINYTEXT",
		"KeyFlag": false
	} ]
}
2

I think if you read the $lookup documentation carefully, you’ll see that the joins there resemble your problem rather closely. All you have to do then is upsert the join into a collection.