Mongodb aggregate - using $and and $eq inside a $match operator - mongodb

Question

I wanted to match and get the documents I wanted based on 2 conditions
data
But it seems like the $eq inside $match isn't doing the right job, I checked the docs many times but can't find what exactly is the problem.
[
{
"episode_title":"Episode Title 1",
"episode_number":"01",
"unique_id":"5D66EEDA9BF055BE80CB997EFD571636C02ED050",
"series_id":1,
"comments_hash":"CBBEA21FE1E4",
"quality":1080,
"thumbnail_url":null,
"thumbnail_version":null,
"original_thumbnail":null,
"watched_by":[
1820242622
]
},
{
"episode_title":"Episode Title 2",
"episode_number":"02",
"unique_id":"12DC0F2B6D1223D8FF6C10189B6CF6DEB4BBA60B",
"series_id":1,
"comments_hash":"EEDA9BF055BE80C",
"quality":720,
"thumbnail_url":null,
"thumbnail_version":null,
"original_thumbnail":null,
"watched_by":[
1820242622
]
},
{
"episode_title":"Episode Title 1",
"episode_number":"01",
"unique_id":"635F12999D0641C95CBBEA21FE1E46BF26BDCCCA",
"series_id":2,
"comments_hash":"7EFD571636",
"quality":1080,
"thumbnail_url":null,
"thumbnail_version":null,
"original_thumbnail":null,
"watched_by":[
1820242622
]
}
]
The data in USERS collection looks something like this:
[
{
"user_id":1820242622,
"full_name":"user 1",
"start_date":"2021-11-18T19:36:27.695953",
"is_banned":false,
"preferred_quality":1080
},
{
"user_id":1820242624,
"full_name":"user 2",
"start_date":"2021-11-18T19:36:27.695953",
"is_banned":false,
"preferred_quality":0
}
]
and I used this code (pymongo):
user_id = 1820242622
series_id = 1
db.data_col.aggregate([
{
"$lookup":{
"from":"USERS",
"pipeline":[
{
"$match":{
"user_id":"user_id"
}
},
{
"$project":{
"preferred_quality":1
}
}
],
"as":"preferred_quality"
}
},
{
"$match":{
"$and":[
{
"$eq":[
"$series_id",
"series_id"
]
},
{
"$in":[
"$quality",
[
0,
"$preferred_quality"
]
]
}
]
}
},
{
"$set":{
"preferred_quality":"$preferred_quality"
}
},
{
"$set":{
"user_watched":{
"$in":[
"user_id",
"$watched_by"
]
}
}
},
{
"$set":{
"watched_by":"$$REMOVE"
}
}
])
but I'm getting:
raise OperationFailure(errmsg, code, response, max_wire_version) pymongo.errors.OperationFailure: unknown top level operator: $eq. If you have a field name that starts with a '$' symbol, consider using $getField or $setField., full error: {'ok': 0.0, 'errmsg': "unknown top level operator: $eq. If you have a field name that starts with a '$' symbol, consider using $getField or $setField.", 'code': 2, 'codeName': 'BadValue', '$clusterTime': {'clusterTime': Timestamp(1648755167, 3), 'signature': {'hash': b"\x81\xd59\xae\x04'\x15\xac0\x08X6\x86\xc8\xa4\xf22\x07\x87\xd2", 'keyId': 7037880200322875408}}, 'operationTime': Timestamp(1648755167, 3)}
I was expecting something like this:
{
"episode_title":"Episode Title 1",
"episode_number":"01",
"unique_id":"635F12999D0641C95CBBEA21FE1E46BF26BDCCCA",
"series_id":1,
"comments_hash":"7EFD571636",
"quality":1080,
"thumbnail_url":null,
"thumbnail_version":null,
"original_thumbnail":null,
"preferred_quality":1080,
"user_watched":false
}

Answer 1

db.data_col.aggregate([
{
$match: {
"unique_id": "635F12999D0641C95CBBEA21FE1E46BF26BDCCCA"
}
},
{
$lookup: {
from: "USERS",
localField: "watched_by",
foreignField: "user_id",
as: "preferred_quality"
}
},
{
$set: {
preferred_quality: {
$first: "$preferred_quality.preferred_quality"
}
}
}
])
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