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Mongo Aggregation With Projection

Given the following document
{
"Id": "MyNormalObjectId",
"CompanyId" : 1234,
"User" :
{
"UserId":4567,
"FirstName":"Tester",
"Lastname":"McCtesterson"
}
}
How do I write my aggregate query to return a list of all unique users in a given company (including first and last name)?
FilterDefinitionBuilder<MyDoc> builder = Builders<MyDoc>.Filter;
var filter = builder .Eq(t => t.CompanyId, companyId);
var aggregate = _col.Aggregate();
aggregate.Match(filter).GroupBy(t=>t.User.UserId, ?????? )
Desired result would be a HashSet of UserMetadata. I've seen a lot of people go straight to BSon for what they need and I can if I HAVE to. Strongly typed is always better.

You can make use of the $addToSet operator inside the $group pipeline stage
to get the desired output.
db.collection.aggregate([
{
"$match": {
"CompanyId": 1234 // Find Conditions go here
}
},
{
"$group": {
"_id": "$CompanyId",
"Users": {
"$addToSet": "$User",
},
},
},
])

MongoDB C# 2.0 upserting sub item in collection [duplicate]

I have documents that looks something like that, with a unique index on bars.name:
{ name: 'foo', bars: [ { name: 'qux', somefield: 1 } ] }
. I want to either update the sub-document where { name: 'foo', 'bars.name': 'qux' } and $set: { 'bars.$.somefield': 2 }, or create a new sub-document with { name: 'qux', somefield: 2 } under { name: 'foo' }.
Is it possible to do this using a single query with upsert, or will I have to issue two separate ones?
Related: 'upsert' in an embedded document (suggests to change the schema to have the sub-document identifier as the key, but this is from two years ago and I'm wondering if there are better solutions now.)

No there isn't really a better solution to this, so perhaps with an explanation.
Suppose you have a document in place that has the structure as you show:
{
"name": "foo",
"bars": [{
"name": "qux",
"somefield": 1
}]
}
If you do an update like this
db.foo.update(
{ "name": "foo", "bars.name": "qux" },
{ "$set": { "bars.$.somefield": 2 } },
{ "upsert": true }
)
Then all is fine because matching document was found. But if you change the value of "bars.name":
db.foo.update(
{ "name": "foo", "bars.name": "xyz" },
{ "$set": { "bars.$.somefield": 2 } },
{ "upsert": true }
)
Then you will get a failure. The only thing that has really changed here is that in MongoDB 2.6 and above the error is a little more succinct:
WriteResult({
"nMatched" : 0,
"nUpserted" : 0,
"nModified" : 0,
"writeError" : {
"code" : 16836,
"errmsg" : "The positional operator did not find the match needed from the query. Unexpanded update: bars.$.somefield"
}
})
That is better in some ways, but you really do not want to "upsert" anyway. What you want to do is add the element to the array where the "name" does not currently exist.
So what you really want is the "result" from the update attempt without the "upsert" flag to see if any documents were affected:
db.foo.update(
{ "name": "foo", "bars.name": "xyz" },
{ "$set": { "bars.$.somefield": 2 } }
)
Yielding in response:
WriteResult({ "nMatched" : 0, "nUpserted" : 0, "nModified" : 0 })
So when the modified documents are 0 then you know you want to issue the following update:
db.foo.update(
{ "name": "foo" },
{ "$push": { "bars": {
"name": "xyz",
"somefield": 2
}}
)
There really is no other way to do exactly what you want. As the additions to the array are not strictly a "set" type of operation, you cannot use $addToSet combined with the "bulk update" functionality there, so that you can "cascade" your update requests.
In this case it seems like you need to check the result, or otherwise accept reading the whole document and checking whether to update or insert a new array element in code.

if you dont mind changing the schema a bit and having a structure like so:
{ "name": "foo", "bars": { "qux": { "somefield": 1 },
"xyz": { "somefield": 2 },
}
}
You can perform your operations in one go.
Reiterating 'upsert' in an embedded document for completeness

I was digging for the same feature, and found that in version 4.2 or above, MongoDB provides a new feature called Update with aggregation pipeline.
This feature, if used with some other techniques, makes possible to achieve an upsert subdocument operation with a single query.
It's a very verbose query, but I believe if you know that you won't have too many records on the subCollection, it's viable. Here's an example on how to achieve this:
const documentQuery = { _id: '123' }
const subDocumentToUpsert = { name: 'xyz', id: '1' }
collection.update(documentQuery, [
{
$set: {
sub_documents: {
$cond: {
if: { $not: ['$sub_documents'] },
then: [subDocumentToUpsert],
else: {
$cond: {
if: { $in: [subDocumentToUpsert.id, '$sub_documents.id'] },
then: {
$map: {
input: '$sub_documents',
as: 'sub_document',
in: {
$cond: {
if: { $eq: ['$$sub_document.id', subDocumentToUpsert.id] },
then: subDocumentToUpsert,
else: '$$sub_document',
},
},
},
},
else: { $concatArrays: ['$sub_documents', [subDocumentToUpsert]] },
},
},
},
},
},
},
])

There's a way to do it in two queries - but it will still work in a bulkWrite.
This is relevant because in my case not being able to batch it is the biggest hangup. With this solution, you don't need to collect the result of the first query, which allows you to do bulk operations if you need to.
Here are the two successive queries to run for your example:
// Update subdocument if existing
collection.updateMany({
name: 'foo', 'bars.name': 'qux'
}, {
$set: {
'bars.$.somefield': 2
}
})
// Insert subdocument otherwise
collection.updateMany({
name: 'foo', $not: {'bars.name': 'qux' }
}, {
$push: {
bars: {
somefield: 2, name: 'qux'
}
}
})
This also has the added benefit of not having corrupted data / race conditions if multiple applications are writing to the database concurrently. You won't risk ending up with two bars: {somefield: 2, name: 'qux'} subdocuments in your document if two applications run the same queries at the same time.

Find if an element in array has value equal to parent element value

Let's say we have a collection of documents like this one:
{
"_id" : ObjectId("591c54faf1c1f419a830b9cf"),
"fingerprint" : "3121733676",
"screewidth" : "1920",
"carts" : [
{
"cartid" : 391796,
"status" : "New",
"cart_created" : ISODate("2017-05-17T13:50:37.388Z"),
"closed" : false,
"items" : [
{
"brandid" : "PIR",
"cai" : "2259700"
}
],
"updatedon" : ISODate("2017-05-17T13:51:24.252Z")
},
{
"cartid" : 422907,
"status" : "New",
"cart_created" : ISODate("2017-10-23T08:57:06.846Z"),
"closed" : false,
"items" : [
{
"brandid" : "PIR",
"cai" : "IrHlNdGtLfBoTlKsJaRySnM195U"
}
],
"updatedon" : ISODate("2017-10-23T09:46:08.579Z")
}
],
"createdon" : ISODate("2016-11-08T10:29:55.120Z"),
"updatedon" : ISODate("2017-10-23T09:46:29.486Z")
}
How do you extract only the documents where no item in the array $.carts have $.carts.closed set to true and $.carts.updatedon greater than $.updatedon minus 3 days ?
I know how to do find all the documents where no item in the array satisfy the condition $and: [closed: {$eq: true}, {updatedon: {$gt : new ISODate("2017-10-20T20:15:31Z")}}]
But how can you reference the parent element $.updatedon for the comparison?
In plain mongodb shell query language it would aleady be of help.
But I am actually accessing it using c# driver, so my query filter is like this:
FilterDefinition<_visitorData> filter;
filter = Builders<_visitorData>.Filter
.Gte(f => f.updatedon, DateTime.Now.AddDays(-15));
filter = filter & (
Builders<_visitorData>.Filter
.Exists(f => f.carts, false)
| !Builders<_visitorData>.Filter.ElemMatch(f =>
f.carts, c => c.closed && c.updatedon > DateTime.Now.AddDays(-15)
)
);
How can I replace DateTime.Now.AddDays(-15) with a reference to the document root element updatedon?

You can project the difference of carts.updatedon and updatedon and then filter out the results from this aggregation pipeline.
coll.aggregate([{'$unwind':'$carts'},
{'$match':{'closed':{'$ne':true}}},
{'$project':{'carts.cartid':1,'carts.status':1,'carts.cart_created':1,'carts.closed':1,'carts.items':1,'carts.updatedon':1,'updatedon':1,'diff':{'$subtract':['$carts.updatedon','$createdon']}}},
{'$match': {'diff': {'$gte': 1000 * 60 * 60 * 24 * days}}}])
days = 3 will filter out results more than 3 days difference documents.
I have just given the example of how you can use $subtract to find date difference and filter documents based on that.

well I was in a similar situation few days back.
I tackled it by using Jobject of Newtonsoft.Json.
Create a function to return bool which actually process each document take it as input.
Jobject jOb=Jobject.parse(<Your document string>);
JArray jAr=JArray.Parse(jOb["carts"]);
If(jOb["updateon"]=<Your Business Validation>)
{
foreach(var item in jAr)
if(item["closed"]==<Your validation>){ return true}
}
return false;
I hope this helps :)
If you handling with any null values in those properties then please use Tryparse and out variable.

mongodb c# set array value in an array

If I have a document with an array that contains arrays, how can I update a field of the second array?
For example, using the MongoDB C# driver, I want to update the field IWantToUpdateThis where the value is John Smith:
{
{
"_id" : 0,
"Guff" : "Blah",
"FirstArray" : [
{
"Blah" : "Guff",
"SecondArray" : [
{
"IWantToUpdateThis" : "John Smith",
"ButNotThis" : "Not me"
},
{
"IWantToUpdateThis" : "Will Smith",
"ButNotThis" : "Not me"
}
]
}
]
} }
I tried various options such as:
var filter = Builders<BsonDocument>.Filter.Eq("FirstArray.SecondArray.IWantToUpdateThis", "John Smith");
var update = Builders<BsonDocument>.Update.Set("FirstArray.SecondArray.$.IWantToUpdateThis", "My New Value");
var result = collection.UpdateOne(filter, update);
But I can't seem to update the value.
Edited to add:
The MongoDB version used when the question was posed was v3.2.12-69-g45cc6d2

I've figured out something that works, but I can't believe it is the best solution to the problem:
var collection = _database.GetCollection<Model>("Stuff");
var filter = Builders<Model>.Filter.Eq("FirstArray.SecondArray.IWantToUpdateThis", OldValue);
var docIds = collection.Find(filter).Project(x => x.Id).ToList();
foreach (var docId in docIds)
{
var model = collection.Find(e => e.Id == docId).FirstOrDefault();
foreach (var first in model.FirstArray)
{
foreach(var second in first.SecondArray)
{
if (second.IWantToUpdateThis == OldValue)
second.IWantToUpdateThis = NewValue;
}
}
collection.ReplaceOne(r => r.Id == docId, model);
}
If anyone comes up with another answer, it is very likely to be a better way than mine, and I leave this answer here only to show a possible way forward should anyone else find themselves in the same dead end as I.

using AND and OR

Trying to get a query that has both AND and OR to work in C#.
In SQL Server would be something like:
... where (Code = 'abc' OR Description = 'def') AND (Flag = 0)
With MongoVUE I seemed to have gotten it to work with this:
{ "$or" : [{ "Description" : /def/i }, { "Code" : /abc/i }], "$and": [{ "Flag" : 0 }] }
but can't seem to get it with the C#:
tried this:
List<IMongoQuery> qryValue = new List<IMongoQuery>();
qryValue.Add(Query.EQ("Code", "abc"));
qryValue.Add(Query.EQ("Description", "def"));
qryValue.Add(Query.And(Query.EQ("Flag", 1)));
var query = Query.Or(qryValue.ToArray());
but get this back:
{ "$or" : [{ "Code" : "abc" }, { "Description" : "def" }, { "Flag" : 1 }] }
and this doesn't give the correct results: missing the AND part.
Anyone can help with this?

You're getting that back because you're are putting all of your Query.EQ into the Query.Or on the last line. Passing in a single value to a Query.And doesn't do anything; it's the same as if you passed a single value to any other method. You haven't and-ed it with anything.
You need to write it in code as you have above in SQL: respect the parenthesis.
Group your Or together first, and pass it as the first parameter to the And, followed by the single, additional clause for Flag.
var clauses = new[] { Query.EQ("Code", "abc"), Query.EQ("Description", "def") };
var query = Query.AND(Query.OR(clauses), Query.EQ("Flag", 1))
Something like that should work.