I’m trying to join or call only one document from multiple documents that can be repeated, all this for a unique identifier, in this case code, which is a numerical value.
[
{
"_id": "6386b0e114fe6aee844af06e",
"transfer": {
"code": 2,
"author": {
"created_at": "2022-11-30T01:29:43.308Z",
"created_by": "userId",
"observation": "It is a long established fact that a reader will be distracted"
},
"output": {
"type": "Transfer out",
"quantity": 3,
"to": {
"warehouse": "6376d84a4587772c3b2d7175",
"warehouse_location": "637d6e218006a7e9609aaf2f",
"expiration_date": "2024-01-03",
"production_lot": "LOT0544522",
"product": "6366a7d99795c333b24f0981"
}
},
"entry": {
"type": "Transfer in",
"quantity": 3,
"from": {
"warehouse": "6376d6c5716fea2e60c491c6",
"warehouse_location": "637d6e1b8006a7e9609aaf2e",
"expiration_date": "2024-01-03",
"production_lot": "LOT0544522",
"product": "6366a7d99795c333b24f0981"
}
}
}
},
{
"_id": "6386b13e14fe6aee844af06f",
"transfer": {
"code": 2,
"author": {
"created_at": "2022-11-30T01:29:43.308Z",
"created_by": "userId",
"observation": "It is a long established fact that a reader will be distracted"
},
"output": {
"type": "Transfer out",
"quantity": 3,
"to": {
"warehouse": "6376d84a4587772c3b2d7175",
"warehouse_location": "637d6e218006a7e9609aaf2f",
"expiration_date": "2024-01-03",
"production_lot": "LOT0544522",
"product": "6366a7d99795c333b24f0981"
}
},
"entry": {
"type": "Transfer in",
"quantity": 3,
"from": {
"warehouse": "6376d6c5716fea2e60c491c6",
"warehouse_location": "637d6e1b8006a7e9609aaf2e",
"expiration_date": "2024-01-03",
"production_lot": "LOT0544522",
"product": "6366a7d99795c333b24f0981"
}
}
}
},
{
"_id": "6386b0e114fe6aee844af06e",
"transfer": {
"code": 1,
"author": {
"created_at": "2022-11-30T01:27:52.003Z",
"created_by": "userId",
"observation": "It is a long established fact that a reader will be distracted"
},
"output": {
"type": "Transfer out",
"quantity": 1,
"to": {
"warehouse": "6376d84a4587772c3b2d7175",
"warehouse_location": "637d6e218006a7e9609aaf2f",
"expiration_date": "2024-01-03",
"production_lot": "LOT0544522",
"product": "6366a7d99795c333b24f0981"
}
},
"entry": {
"type": "Transfer in",
"quantity": 1,
"from": {
"warehouse": "6376d6c5716fea2e60c491c6",
"warehouse_location": "637d6e1b8006a7e9609aaf2e",
"expiration_date": "2024-01-03",
"production_lot": "LOT0544522",
"product": "6366a7d99795c333b24f0981"
}
}
}
},
{
"_id": "6386b13e14fe6aee844af06f",
"transfer": {
"code": 1,
"author": {
"created_at": "2022-11-30T01:27:52.003Z",
"created_by": "userId",
"observation": "It is a long established fact that a reader will be distracted"
},
"output": {
"type": "Transfer out",
"quantity": 1,
"to": {
"warehouse": "6376d84a4587772c3b2d7175",
"warehouse_location": "637d6e218006a7e9609aaf2f",
"expiration_date": "2024-01-03",
"production_lot": "LOT0544522",
"product": "6366a7d99795c333b24f0981"
}
},
"entry": {
"type": "Transfer in",
"quantity": 1,
"from": {
"warehouse": "6376d6c5716fea2e60c491c6",
"warehouse_location": "637d6e1b8006a7e9609aaf2e",
"expiration_date": "2024-01-03",
"production_lot": "LOT0544522",
"product": "6366a7d99795c333b24f0981"
}
}
}
}
]
In this case I only need to retrieve one of the two documents that exist in the collection. code: 1 and code:2 to be displayed, something like this:
[
{
"_id": "6386b0e114fe6aee844af06e",
"transfer": {
"code": 2,
"author": {
"created_at": "2022-11-30T01:29:43.308Z",
"created_by": "userId",
"observation": "It is a long established fact that a reader will be distracted"
},
"output": {
"type": "Transfer out",
"quantity": 3,
"to": {
"warehouse": "6376d84a4587772c3b2d7175",
"warehouse_location": "637d6e218006a7e9609aaf2f",
"expiration_date": "2024-01-03",
"production_lot": "LOT0544522",
"product": "6366a7d99795c333b24f0981"
}
},
"entry": {
"type": "Transfer in",
"quantity": 3,
"from": {
"warehouse": "6376d6c5716fea2e60c491c6",
"warehouse_location": "637d6e1b8006a7e9609aaf2e",
"expiration_date": "2024-01-03",
"production_lot": "LOT0544522",
"product": "6366a7d99795c333b24f0981"
}
}
}
},
{
"_id": "6386b13e14fe6aee844af06f",
"transfer": {
"code": 1,
"author": {
"created_at": "2022-11-30T01:27:52.003Z",
"created_by": "userId",
"observation": "It is a long established fact that a reader will be distracted"
},
"output": {
"type": "Transfer out",
"quantity": 1,
"to": {
"warehouse": "6376d84a4587772c3b2d7175",
"warehouse_location": "637d6e218006a7e9609aaf2f",
"expiration_date": "2024-01-03",
"production_lot": "LOT0544522",
"product": "6366a7d99795c333b24f0981"
}
},
"entry": {
"type": "Transfer in",
"quantity": 1,
"from": {
"warehouse": "6376d6c5716fea2e60c491c6",
"warehouse_location": "637d6e1b8006a7e9609aaf2e",
"expiration_date": "2024-01-03",
"production_lot": "LOT0544522",
"product": "6366a7d99795c333b24f0981"
}
}
}
}
]
The original nomenclature of the object corresponds to the following,
[
{
"_id": "6386b13e14fe6aee844af06f",
"product": "6366a7d99795c333b24f0981",
"warehouse": "6376d84a4587772c3b2d7175",
"warehouse_location": "637d6e218006a7e9609aaf2f",
"production_lot": "LOT0544522",
"expiration_date": "2024-01-03",
"quantity": 12,
"is_deleted": false,
"movements": {
"entries": [...],
"transfers": [
{
"code": 1,
"author": {
"created_at": "2022-11-30T01:27:52.003Z",
"created_by": "userId",
"observation": "It is a long established fact that a reader will be distracted"
},
"output": {
"type": "Transfer out",
"quantity": 1,
"to": {
"warehouse": "6376d84a4587772c3b2d7175",
"warehouse_location": "637d6e218006a7e9609aaf2f",
"expiration_date": "2024-01-03",
"production_lot": "LOT0544522",
"product": "6366a7d99795c333b24f0981"
}
},
"entry": {
"type": "Transfer in",
"quantity": 1,
"from": {
"warehouse": "6376d6c5716fea2e60c491c6",
"warehouse_location": "637d6e1b8006a7e9609aaf2e",
"expiration_date": "2024-01-03",
"production_lot": "LOT0544522",
"product": "6366a7d99795c333b24f0981"
}
}
},
{
"code": 2,
"author": {
"created_at": "2022-11-30T01:29:43.308Z",
"created_by": "userId",
"observation": "It is a long established fact that a reader will be distracted"
},
"output": {
"type": "Transfer out",
"quantity": 3,
"to": {
"warehouse": "6376d84a4587772c3b2d7175",
"warehouse_location": "637d6e218006a7e9609aaf2f",
"expiration_date": "2024-01-03",
"production_lot": "LOT0544522",
"product": "6366a7d99795c333b24f0981"
}
},
"entry": {
"type": "Transfer in",
"quantity": 3,
"from": {
"warehouse": "6376d6c5716fea2e60c491c6",
"warehouse_location": "637d6e1b8006a7e9609aaf2e",
"expiration_date": "2024-01-03",
"production_lot": "LOT0544522",
"product": "6366a7d99795c333b24f0981"
}
}
}
]
}
},
{
"_id": "6386b0e114fe6aee844af06e",
"product": "6366a7d99795c333b24f0981",
"warehouse": "6376d6c5716fea2e60c491c6",
"warehouse_location": "637d6e1b8006a7e9609aaf2e",
"production_lot": "LOT0544522",
"expiration_date": "2024-01-03",
"quantity": 11,
"is_deleted": false,
"movements": {
"entries": [...],
"outputs": [...],
"transfers": [
{
"code": 1,
"author": {
"created_at": "2022-11-30T01:27:52.003Z",
"created_by": "userId",
"observation": "It is a long established fact that a reader will be distracted"
},
"output": {
"type": "Transfer out",
"quantity": 1,
"to": {
"warehouse": "6376d84a4587772c3b2d7175",
"warehouse_location": "637d6e218006a7e9609aaf2f",
"expiration_date": "2024-01-03",
"production_lot": "LOT0544522",
"product": "6366a7d99795c333b24f0981"
}
},
"entry": {
"type": "Transfer in",
"quantity": 1,
"from": {
"warehouse": "6376d6c5716fea2e60c491c6",
"warehouse_location": "637d6e1b8006a7e9609aaf2e",
"expiration_date": "2024-01-03",
"production_lot": "LOT0544522",
"product": "6366a7d99795c333b24f0981"
}
}
},
{
"code": 2,
"author": {
"created_at": "2022-11-30T01:29:43.308Z",
"created_by": "userId",
"observation": "It is a long established fact that a reader will be distracted"
},
"output": {
"type": "Transfer out",
"quantity": 3,
"to": {
"warehouse": "6376d84a4587772c3b2d7175",
"warehouse_location": "637d6e218006a7e9609aaf2f",
"expiration_date": "2024-01-03",
"production_lot": "LOT0544522",
"product": "6366a7d99795c333b24f0981"
}
},
"entry": {
"type": "Transfer in",
"quantity": 3,
"from": {
"warehouse": "6376d6c5716fea2e60c491c6",
"warehouse_location": "637d6e1b8006a7e9609aaf2e",
"expiration_date": "2024-01-03",
"production_lot": "LOT0544522",
"product": "6366a7d99795c333b24f0981"
}
}
}
]
}
}
]
For this reason, what I do is get to the level of each type of movement, be it transfer, inventory inputs or outputs, and I do it as follows:
return this.connect().then((db) => {
return (
db
.collection(collection)
// The following aggregation uses the $unwind stage to output a
// document for each element in the movements.outputs array
.aggregate([
// Stage 1
{ $unwind: '$movements' },
// Stage 2
{ $unwind: '$movements.transfers' },
// Group by code field
{
$group: {
code: ...,
},
},
])
// The following project only returns the movements.transfers object
.project({
transfer: '$movements.transfers',
})
.sort({ 'transfer.code': -1 })
.toArray()
);
});
I have tried to use merge or group but have not been able to do what I expect based on the code parameter. Any other way to achieve this?
2
Answers
Use Sample https://www.mongodb.com/docs/manual/reference/operator/aggregation/sample/
Add this to your query
One option is to add two steps to your aggregation pipeline:
See how it works on the playground example
But there is no much point in
$unwindand then$groupagain just after. if you share a simplified version of your documents before the$unwindsteps, and the requested result for them, we can see how to optimize this query before the current step.