To directly answer your question, yes it is the most efficient way. But I do think we need to clarify why this is so. As was suggested in alternatives, the one thing people are looking at is “sorting” your results before passing to a $group stage and what they are looking at is the “timestamp” … Read more
Sum To get the sum of a grouped field when using the Aggregation Framework of MongoDB, you’ll need to use $group and $sum: db.characters.aggregate([ { $group: { _id: null, total: { $sum: “$wins” } } } ] ) In this case, if you want to get the sum of all of the wins, you need … Read more
The cause of your ‘troubles’ is the second aggregation stage – { $unwind: “$address” }. It removes record for party with _id: 4 (because its address array is empty, as you mention) and produces two records for parties _id: 1 and _id: 5 (because each of them has two addresses). To prevent removing of parties … Read more
Thanks @Neil Lunn Update mongoose. Mongoose versions prior to 5.0 are incorrectly matched for MongoDB 3.6. MongoDB 3.6 changed the aggregate API from “cursor optional” to “cursor only”, and older mongoose versions break this by trying to invoke a deprecated way to ask for an array in response.
Congratulations, you appear to have found a bug. This only happens with MongoDB 3.0.0 in my testing, or at least is not present at MongoDB 2.6.6. Bug now recorded at SERVER-17599 NOTE: Not actually an “issue” but confirmed “by design”. Dropped the option for version 3.0.0. Still listed in the documentation though. The problem is … Read more
The query you want is this: db.collection.find({“users”:{“$not”:{“$elemMatch”:{“user”:{$nin:[1,5,7]}}}}}) This says find me all documents that don’t have elements that are outside of the list 1,5,7.
If you are wanting to do a pattern match on numbers, the way to do it in mongo is use the $where expression and pass in a pattern match. > db.test.find({ $where: “/^123.*/.test(this.example)” }) { “_id” : ObjectId(“4bfc3187fec861325f34b132”), “example” : 1234 }
Using MongoDB 4.0 and newer The $toDate operator will convert the value to a date. If the value cannot be converted to a date, $toDate errors. If the value is null or missing, $toDate returns null: You can use it within an aggregate pipeline as follows: db.collection.aggregate([ { “$addFields”: { “created_at”: { “$toDate”: “$created_at” } … Read more
So the query you have actually selects the “document” just like it should. But what you are looking for is to “filter the arrays” contained so that the elements returned only match the condition of the query. The real answer is of course that unless you are really saving a lot of bandwidth by filtering … Read more
As stated earlier in comment, the error occurs because when performing the $lookup which by default produces a target “array” within the parent document from the results of the foreign collection, the total size of documents selected for that array causes the parent to exceed the 16MB BSON Limit. The counter for this is to … Read more