How to remove an array value from item in a nested document array - mongodb

I want to remove "tag4" only for "user3":
{
_id: "doc"
some: "value",
users: [
{
_id: "user3",
someOther: "value",
tags: [
"tag4",
"tag2"
]
}, {
_id: "user1",
someOther: "value",
tags: [
"tag3",
"tag4"
]
}
]
},
{
...
}
Note: This collection holds items referencing many users. Users are stored in a different collection. Unique tags for each user are also stored in the users collection. If an user removes a tag (or multiple) from his account it should be deleted from all items.
I tried this query, but it removes "tag4" for all users:
{
"users._id": "user3",
"users.tags": {
$in: ["tag4"]
}
}, {
$pullAll: {
"users.$.tags": ["tag4"]
}
}, {
multi: 1
}
I tried $elemMatch (and $and) in the selector but ended up with the same result only on the first matching document or noticed some strange things happen (sometimes all tags of other users are deleted).
Any ideas how to solve this? Is there a way to "back reference" in $pull conditions?


You need to use $elemMatch in your query object so that it will only match if both the _id and tags parts match for the same element:
db.test.update({
users: {$elemMatch: {_id: "user3", tags: {$in: ["tag4"]}}}
}, {
$pullAll: {
"users.$.tags": ["tag4"]
}
}, {
multi: 1
})

Related

Conditionally set element of array or push new element in mongo update [duplicate]

I have the following collection
{
"_id" : ObjectId("57315ba4846dd82425ca2408"),
"myarray" : [
{
userId : ObjectId("570ca5e48dbe673802c2d035"),
point : 5
},
{
userId : ObjectId("613ca5e48dbe673802c2d521"),
point : 2
},
]
}
These are my questions
I want to push into myarray if userId doesn't exist, it should be appended to myarray. If userId exists, it should be updated to point.
I found this
db.collection.update({
_id : ObjectId("57315ba4846dd82425ca2408"),
"myarray.userId" : ObjectId("570ca5e48dbe673802c2d035")
}, {
$set: { "myarray.$.point": 10 }
})
But if userId doesn't exist, nothing happens.
and
db.collection.update({
_id : ObjectId("57315ba4846dd82425ca2408")
}, {
$push: {
"myarray": {
userId: ObjectId("570ca5e48dbe673802c2d035"),
point: 10
}
}
})
But if userId object already exists, it will push again.
What is the best way to do this in MongoDB?

Try this
db.collection.update(
{ _id : ObjectId("57315ba4846dd82425ca2408")},
{ $pull: {"myarray.userId": ObjectId("570ca5e48dbe673802c2d035")}}
)
db.collection.update(
{ _id : ObjectId("57315ba4846dd82425ca2408")},
{ $push: {"myarray": {
userId:ObjectId("570ca5e48dbe673802c2d035"),
point: 10
}}
)
Explination:
in the first statment $pull removes the element with userId= ObjectId("570ca5e48dbe673802c2d035") from the array on the document where _id = ObjectId("57315ba4846dd82425ca2408")
In the second one $push inserts
this object { userId:ObjectId("570ca5e48dbe673802c2d035"), point: 10 } in the same array.

The accepted answer by Flying Fisher is that the existing record will first be deleted, and then it will be pushed again.
A safer approach (common sense) would be to try to update the record first, and if that did not find a match, insert it, like so:
// first try to overwrite existing value
var result = db.collection.update(
{
_id : ObjectId("57315ba4846dd82425ca2408"),
"myarray.userId": ObjectId("570ca5e48dbe673802c2d035")
},
{
$set: {"myarray.$.point": {point: 10}}
}
);
// you probably need to modify the following if-statement to some async callback
// checking depending on your server-side code and mongodb-driver
if(!result.nMatched)
{
// record not found, so create a new entry
// this can be done using $addToSet:
db.collection.update(
{
_id: ObjectId("57315ba4846dd82425ca2408")
},
{
$addToSet: {
myarray: {
userId: ObjectId("570ca5e48dbe673802c2d035"),
point: 10
}
}
}
);
// OR (the equivalent) using $push:
db.collection.update(
{
_id: ObjectId("57315ba4846dd82425ca2408"),
"myarray.userId": {$ne: ObjectId("570ca5e48dbe673802c2d035"}}
},
{
$push: {
myarray: {
userId: ObjectId("570ca5e48dbe673802c2d035"),
point: 10
}
}
}
);
}
This should also give (common sense, untested) an increase in performance, if in most cases the record already exists, only the first query will be executed.

There is a option called update documents with aggregation pipeline starting from MongoDB v4.2,
check condition $cond if userId in myarray.userId or not
if yes then $map to iterate loop of myarray array and check condition if userId match then merge with new document using $mergeObjects
if no then $concatArrays to concat new object and myarray
let _id = ObjectId("57315ba4846dd82425ca2408");
let updateDoc = {
userId: ObjectId("570ca5e48dbe673802c2d035"),
point: 10
};
db.collection.update(
{ _id: _id },
[{
$set: {
myarray: {
$cond: [
{ $in: [updateDoc.userId, "$myarray.userId"] },
{
$map: {
input: "$myarray",
in: {
$mergeObjects: [
"$$this",
{
$cond: [
{ $eq: ["$$this.userId", updateDoc.userId] },
updateDoc,
{}
]
}
]
}
}
},
{ $concatArrays: ["$myarray", [updateDoc]] }
]
}
}
}]
)
Playground

Unfortunately "upsert" operation is not possible on embedded array. Operators simply do not exist so that this is not possible in a single statement.Hence you must perform two update operations in order to do what you want. Also the order of application for these two updates is important to get desired result.

I haven't found any solutions based on a one atomic query. Instead there are 3 ways based on a sequence of two queries:
always $pull (to remove the item from array), then $push (to add the updated item to array)
db.collection.update(
{ _id : ObjectId("57315ba4846dd82425ca2408")},
{ $pull: {"myarray.userId": ObjectId("570ca5e48dbe673802c2d035")}}
)
db.collection.update(
{ _id : ObjectId("57315ba4846dd82425ca2408")},
{
$push: {
"myarray": {
userId:ObjectId("570ca5e48dbe673802c2d035"),
point: 10
}
}
}
)
try to $set (to update the item in array if exists), then get the result and check if the updating operation successed or if a $push needs (to insert the item)
var result = db.collection.update(
{
_id : ObjectId("57315ba4846dd82425ca2408"),
"myarray.userId": ObjectId("570ca5e48dbe673802c2d035")
},
{
$set: {"myarray.$.point": {point: 10}}
}
);
if(!result.nMatched){
db.collection.update({_id: ObjectId("57315ba4846dd82425ca2408")},
{
$addToSet: {
myarray: {
userId: ObjectId("570ca5e48dbe673802c2d035"),
point: 10
}
}
);
always $addToSet (to add the item if not exists), then always $set to update the item in array
db.collection.update({_id: ObjectId("57315ba4846dd82425ca2408")},
myarray: { $not: { $elemMatch: {userId: ObjectId("570ca5e48dbe673802c2d035")} } } },
{
$addToSet : {
myarray: {
userId: ObjectId("570ca5e48dbe673802c2d035"),
point: 10
}
}
},
{ multi: false, upsert: false});
db.collection.update({
_id: ObjectId("57315ba4846dd82425ca2408"),
"myArray.userId": ObjectId("570ca5e48dbe673802c2d035")
},
{ $set : { myArray.$.point: 10 } },
{ multi: false, upsert: false});
1st and 2nd way are unsafe, so transaction must be established to avoid two concurrent requests could push the same item generating a duplicate.
3rd way is safer. the $addToSet adds only if the item doesn't exist, otherwise nothing happens. In case of two concurrent requests, only one of them adds the missing item to the array.

Possible solution with aggregation pipeline:
db.collection.update(
{ _id },
[
{
$set: {
myarray: { $filter: {
input: '$myarray',
as: 'myarray',
cond: { $ne: ['$$myarray.userId', ObjectId('570ca5e48dbe673802c2d035')] },
} },
},
},
{
$set: {
myarray: {
$concatArrays: [
'$myarray',
[{ userId: ObjectId('570ca5e48dbe673802c2d035'), point: 10 },
],
],
},
},
},
],
);
We use 2 stages:
filter myarray (= remove element if userId exist)
concat filtered myarray with new element;

When you want update or insert value in array try it
Object in db
key:name,
key1:name1,
arr:[
{
val:1,
val2:1
}
]
Query
var query = {
$inc:{
"arr.0.val": 2,
"arr.0.val2": 2
}
}
.updateOne( { "key": name }, query, { upsert: true }
key:name,
key1:name1,
arr:[
{
val:3,
val2:3
}
]

In MongoDB 3.6 it is now possible to upsert elements in an array.

array update and create don't mix in under one query, if you care much about atomicity then there's this solution:
normalise your schema to,
{
"_id" : ObjectId("57315ba4846dd82425ca2408"),
userId : ObjectId("570ca5e48dbe673802c2d035"),
point : 5
}

You could use a variation of the .forEach/.updateOne method I currently use in mongosh CLI to do things like that. In the .forEach, you might be able to set all of your if/then conditions that you mentioned.
Example of .forEach/.updateOne:
let medications = db.medications.aggregate([
{$match: {patient_id: {$exists: true}}}
]).toArray();
medications.forEach(med => {
try {
db.patients.updateOne({patient_id: med.patient_id},
{$push: {medications: med}}
)
} catch {
console.log("Didn't find match for patient_id. Could not add this med to a patient.")
}
})
This may not be the most "MongoDB way" to do it, but it definitely works and gives you the freedom of javascript to do things within the .forEach.

delete element out of array with $pull and $cond operators

I want to pull elements out of the array only if some condition is met
This is my document structure:
{
_id: "userId",
posts: [{
_id: "postId",
comments:[{
_id: "commentId",
userid: "some id of an user" // USER
},{
_id: "commentId2",
userid: "some id of an user2"
}]
}]
}
I want to delete the element from the comments array with the given commentId. This should be done only if userid is USER. If that condition isn't met, that means that comment doesn't belongs to the user that wants to delete it so I decline it.
Tried Attempt :
Post.findOneAndUpdate(
{
_id: mongoose.Types.ObjectId(userId)
},
{
$pull: {
$cond: [
{
"posts.$[post].comments.$[comment].userid": {
$eq: USER
}
},
{
$pull: {
comments: {
_id: mongoose.Types.ObjectId(commentId)
}
}
}
]
}
},
{
arrayFilters: [
{
"comment._id": mongoose.Types.ObjectId(commentId)
},
{
"post._id": mongoose.Types.ObjectId(postId)
}
]
}
)
That code above doesn't work, I'm stuck there & I don't know how to continue. maybe somebody knows how to fix this.

You can try below query :
Post.findOneAndUpdate(
{
_id: mongoose.Types.ObjectId(userId) // Fetches actual document
},
// Any matching object that has these fields/values in comments array will be pulled out
{
$pull: {"posts.$[post].comments": { _id : mongoose.Types.ObjectId(commentId), "userid": USER }}},
{
arrayFilters: [
{
"post._id": mongoose.Types.ObjectId(postId) // Checks which object inside `posts` array needs to be updated
}
]
}
)
Note : Use an option { new : true } in mongoose to return updated document, or in shell use { returnNewDocument : true }

Mongoose get only specific object from array or empty array if there is none

So I have a questionnaire model:
const schema = new mongoose.Schema({
title: String,
category: String,
description: String,
requirementOption: String,
creationDate: String,
questions: [],
answers: []
})
As you can see the answers is an array. This array contains object that have this structure
{
"participantEmail": "someEmail#email.email"
"currentIndex": 14,
...
}
Now I want to get a specific questionnaire by id, but in answers array I only want specific participant email. So the answers array should have either one element or no element. But I don't want to get null result if there is no such email in the answers array.
I figure it out how to get that specific element from array with this query:
dbModel.findOne({_id: id, 'answers': {$elemMatch: {participantEmail: "someEmail#email.com"}}}, {'answers.$': 1}).exec();
And if that email exists in the answer array I will get this:
"data": {
"questionnaireForParticipant": {
"id": "5d9ca298cba039001b916c55",
"title": null,
"category": null,
"creationDate": null,
"description": null,
"questions": null,
"answers": [
{
"participantEmail": "someEmail#email.com",
....
}
}
}
But if that email is not in the answers array I will get only null. Also I would like to get the title and category and all of the other fields. But I can't seem to find a way to do this.

Since you've this condition 'answers': {$elemMatch: {participantEmail: "someEmail#email.com"}} in filter part of .findOne() - If for given _id document there are no elements in answers. participantEmail array match with input value "someEmail#email.com" then .findOne() will return null as output. So if you wanted to return document irrespective of a matching element exists in answers array or not then try below query :
db.collection.aggregate([
{
$match: { "_id": ObjectId("5a934e000102030405000000") }
},
/** addFields will re-create an existing field or will create new field if there is no field with same name */
{
$addFields: {
answers: {
$filter: { // filter will result in either [] or array with matching elements
input: "$answers",
cond: { $eq: [ "$$this.participantEmail", "someEmail#email.com" ] }
}
}
}
}
])
Test : mongoplayground
Ref : aggregation-pipeline
Note : We've used aggregation as you wanted to return either answers array with matched element or an empty array. Also you can use $project instead of $addFields to transform the output as you wanted to.

The accepted answer is correct, but if you are using mongoose like I do this is how you have to write the accepted answer query:
dbModel.aggregate([
{
$match: { "_id": mongoose.Types.ObjectId("5a934e000102030405000000") }
}]).addFields({
answers: {
$filter: {
input: "$answers",
cond: { $eq: [ "$$this.participantEmail", "someEmail#email.com" ] }
}
}
}).exec();

With this sample input document:
{
_id: 1,
title: "t-1",
category: "cat-abc",
creationDate: ISODate("2020-05-05T07:01:09.853Z"),
questions: [ ],
answers: [
{ participantEmail: "someEmail#email.email", currentIndex: 14 }
]
}
And, with this query:
EMAIL_TO_MATCH = "someEmail#email.email"
db.questionnaire.findOne(
{ _id: 1 },
{ title: 1, category: 1, answers: { $elemMatch: { participantEmail: EMAIL_TO_MATCH } } }
)
The query returns (when the answers.participantEmail matches):
{
"_id" : 1,
"title" : "t-1",
"category" : "cat-abc",
"answers" : [
{
"participantEmail" : "someEmail#email.email",
"currentIndex" : 12
}
]
}
And, when the answers.participantEmail doesn't match or if the amswers array is empty, the result is:
{ "_id" : 1, "title" : "t-1", "category" : "cat-abc" }
NOTE: The $elemMatch used in the above query is a projection operator.

MongoDB - Update or Insert object in array

I have the following collection
{
"_id" : ObjectId("57315ba4846dd82425ca2408"),
"myarray" : [
{
userId : ObjectId("570ca5e48dbe673802c2d035"),
point : 5
},
{
userId : ObjectId("613ca5e48dbe673802c2d521"),
point : 2
},
]
}
These are my questions
I want to push into myarray if userId doesn't exist, it should be appended to myarray. If userId exists, it should be updated to point.
I found this
db.collection.update({
_id : ObjectId("57315ba4846dd82425ca2408"),
"myarray.userId" : ObjectId("570ca5e48dbe673802c2d035")
}, {
$set: { "myarray.$.point": 10 }
})
But if userId doesn't exist, nothing happens.
and
db.collection.update({
_id : ObjectId("57315ba4846dd82425ca2408")
}, {
$push: {
"myarray": {
userId: ObjectId("570ca5e48dbe673802c2d035"),
point: 10
}
}
})
But if userId object already exists, it will push again.
What is the best way to do this in MongoDB?

Try this
db.collection.update(
{ _id : ObjectId("57315ba4846dd82425ca2408")},
{ $pull: {"myarray.userId": ObjectId("570ca5e48dbe673802c2d035")}}
)
db.collection.update(
{ _id : ObjectId("57315ba4846dd82425ca2408")},
{ $push: {"myarray": {
userId:ObjectId("570ca5e48dbe673802c2d035"),
point: 10
}}
)
Explination:
in the first statment $pull removes the element with userId= ObjectId("570ca5e48dbe673802c2d035") from the array on the document where _id = ObjectId("57315ba4846dd82425ca2408")
In the second one $push inserts
this object { userId:ObjectId("570ca5e48dbe673802c2d035"), point: 10 } in the same array.

The accepted answer by Flying Fisher is that the existing record will first be deleted, and then it will be pushed again.
A safer approach (common sense) would be to try to update the record first, and if that did not find a match, insert it, like so:
// first try to overwrite existing value
var result = db.collection.update(
{
_id : ObjectId("57315ba4846dd82425ca2408"),
"myarray.userId": ObjectId("570ca5e48dbe673802c2d035")
},
{
$set: {"myarray.$.point": {point: 10}}
}
);
// you probably need to modify the following if-statement to some async callback
// checking depending on your server-side code and mongodb-driver
if(!result.nMatched)
{
// record not found, so create a new entry
// this can be done using $addToSet:
db.collection.update(
{
_id: ObjectId("57315ba4846dd82425ca2408")
},
{
$addToSet: {
myarray: {
userId: ObjectId("570ca5e48dbe673802c2d035"),
point: 10
}
}
}
);
// OR (the equivalent) using $push:
db.collection.update(
{
_id: ObjectId("57315ba4846dd82425ca2408"),
"myarray.userId": {$ne: ObjectId("570ca5e48dbe673802c2d035"}}
},
{
$push: {
myarray: {
userId: ObjectId("570ca5e48dbe673802c2d035"),
point: 10
}
}
}
);
}
This should also give (common sense, untested) an increase in performance, if in most cases the record already exists, only the first query will be executed.

There is a option called update documents with aggregation pipeline starting from MongoDB v4.2,
check condition $cond if userId in myarray.userId or not
if yes then $map to iterate loop of myarray array and check condition if userId match then merge with new document using $mergeObjects
if no then $concatArrays to concat new object and myarray
let _id = ObjectId("57315ba4846dd82425ca2408");
let updateDoc = {
userId: ObjectId("570ca5e48dbe673802c2d035"),
point: 10
};
db.collection.update(
{ _id: _id },
[{
$set: {
myarray: {
$cond: [
{ $in: [updateDoc.userId, "$myarray.userId"] },
{
$map: {
input: "$myarray",
in: {
$mergeObjects: [
"$$this",
{
$cond: [
{ $eq: ["$$this.userId", updateDoc.userId] },
updateDoc,
{}
]
}
]
}
}
},
{ $concatArrays: ["$myarray", [updateDoc]] }
]
}
}
}]
)
Playground

Unfortunately "upsert" operation is not possible on embedded array. Operators simply do not exist so that this is not possible in a single statement.Hence you must perform two update operations in order to do what you want. Also the order of application for these two updates is important to get desired result.

I haven't found any solutions based on a one atomic query. Instead there are 3 ways based on a sequence of two queries:
always $pull (to remove the item from array), then $push (to add the updated item to array)
db.collection.update(
{ _id : ObjectId("57315ba4846dd82425ca2408")},
{ $pull: {"myarray.userId": ObjectId("570ca5e48dbe673802c2d035")}}
)
db.collection.update(
{ _id : ObjectId("57315ba4846dd82425ca2408")},
{
$push: {
"myarray": {
userId:ObjectId("570ca5e48dbe673802c2d035"),
point: 10
}
}
}
)
try to $set (to update the item in array if exists), then get the result and check if the updating operation successed or if a $push needs (to insert the item)
var result = db.collection.update(
{
_id : ObjectId("57315ba4846dd82425ca2408"),
"myarray.userId": ObjectId("570ca5e48dbe673802c2d035")
},
{
$set: {"myarray.$.point": {point: 10}}
}
);
if(!result.nMatched){
db.collection.update({_id: ObjectId("57315ba4846dd82425ca2408")},
{
$addToSet: {
myarray: {
userId: ObjectId("570ca5e48dbe673802c2d035"),
point: 10
}
}
);
always $addToSet (to add the item if not exists), then always $set to update the item in array
db.collection.update({_id: ObjectId("57315ba4846dd82425ca2408")},
myarray: { $not: { $elemMatch: {userId: ObjectId("570ca5e48dbe673802c2d035")} } } },
{
$addToSet : {
myarray: {
userId: ObjectId("570ca5e48dbe673802c2d035"),
point: 10
}
}
},
{ multi: false, upsert: false});
db.collection.update({
_id: ObjectId("57315ba4846dd82425ca2408"),
"myArray.userId": ObjectId("570ca5e48dbe673802c2d035")
},
{ $set : { myArray.$.point: 10 } },
{ multi: false, upsert: false});
1st and 2nd way are unsafe, so transaction must be established to avoid two concurrent requests could push the same item generating a duplicate.
3rd way is safer. the $addToSet adds only if the item doesn't exist, otherwise nothing happens. In case of two concurrent requests, only one of them adds the missing item to the array.

Possible solution with aggregation pipeline:
db.collection.update(
{ _id },
[
{
$set: {
myarray: { $filter: {
input: '$myarray',
as: 'myarray',
cond: { $ne: ['$$myarray.userId', ObjectId('570ca5e48dbe673802c2d035')] },
} },
},
},
{
$set: {
myarray: {
$concatArrays: [
'$myarray',
[{ userId: ObjectId('570ca5e48dbe673802c2d035'), point: 10 },
],
],
},
},
},
],
);
We use 2 stages:
filter myarray (= remove element if userId exist)
concat filtered myarray with new element;

When you want update or insert value in array try it
Object in db
key:name,
key1:name1,
arr:[
{
val:1,
val2:1
}
]
Query
var query = {
$inc:{
"arr.0.val": 2,
"arr.0.val2": 2
}
}
.updateOne( { "key": name }, query, { upsert: true }
key:name,
key1:name1,
arr:[
{
val:3,
val2:3
}
]

In MongoDB 3.6 it is now possible to upsert elements in an array.

array update and create don't mix in under one query, if you care much about atomicity then there's this solution:
normalise your schema to,
{
"_id" : ObjectId("57315ba4846dd82425ca2408"),
userId : ObjectId("570ca5e48dbe673802c2d035"),
point : 5
}

You could use a variation of the .forEach/.updateOne method I currently use in mongosh CLI to do things like that. In the .forEach, you might be able to set all of your if/then conditions that you mentioned.
Example of .forEach/.updateOne:
let medications = db.medications.aggregate([
{$match: {patient_id: {$exists: true}}}
]).toArray();
medications.forEach(med => {
try {
db.patients.updateOne({patient_id: med.patient_id},
{$push: {medications: med}}
)
} catch {
console.log("Didn't find match for patient_id. Could not add this med to a patient.")
}
})
This may not be the most "MongoDB way" to do it, but it definitely works and gives you the freedom of javascript to do things within the .forEach.

Add field (boolean) to returned objects, when a specified value is in array, without including the array itself

I have a mongoose Schema that looks likes this :
var AnswerSchema = new Schema({
author: {type: Schema.Types.ObjectId, ref: 'User'},
likes: [{type: Schema.Types.ObjectId, ref: 'User'}]
text: String,
....
});
and I have an API endpoint that allow to get answers posted by a specific user (which exclude the likes array). What I want to do is add a field (with "true/false" value for example) to the answer(s) returned by the mongoose query, when a specific user_id is (or is not) in the likes array of an answer. This way, I can display to the user requesting the answers if he already liked an answer or not.
How could I achieve this in an optimised way ? I would like to avoid fetching the likes array, then look into it myself in my Javascript code to check if specified userId is present in it, then remove it before sending it back to the client... because it sounds wrong to fetch all this data from mongoDB to my node app for nothing. I'm sure there is a better way by using aggregation but I never used it and am a bit confused on how to do it right.
The database might grow very large so it must be quick and optimised.

One approach you could take is via the aggregation framework which allows you to add/modify fields via the $project pipeline, applying a host of logical operators that work in cohort to achieve the desired end result. For instance, in your above case this would translate to:
Answer.aggregate()
.project({
"author": 1,
"matched": {
"$eq": [
{
"$size": {
"$ifNull": [
{ "$setIntersection": [ "$likes", [userId] ] },
[]
]
}
},
1
]
}
})
.exec(function (err, docs){
console.log(docs);
})
As an example to test in mongo shell, let's insert some few test documents to the test collection:
db.test.insert([
{
"likes": [1, 2, 3]
},
{
"likes": [3, 2]
},
{
"likes": null
},
{
"another": "foo"
}
])
Running the above aggregation pipeline on the test collection to get the boolean field for userId = 2:
var userId = 2;
db.test.aggregate([
{
"$project": {
"matched": {
"$eq": [
{
"$size": {
"$ifNull": [
{ "$setIntersection": [ "$likes", [userId] ] },
[]
]
}
},
1
]
}
}
}
])
gives the following output:
{
"result" : [
{
"_id" : ObjectId("564f487c7d3c273d063cd21e"),
"matched" : true
},
{
"_id" : ObjectId("564f487c7d3c273d063cd21f"),
"matched" : true
},
{
"_id" : ObjectId("564f487c7d3c273d063cd220"),
"matched" : false
},
{
"_id" : ObjectId("564f487c7d3c273d063cd221"),
"matched" : false
}
],
"ok" : 1
}