Related
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.
Lets say I have the following collection
{
_id:1,
item:"cat"
keywords:['A','B']
},
{
_id:2,
item:"cat"
keywords:['B','C']
},
{
_id:3,
item:"dog"
keywords:['C','D']
},
I would like to get the following results:
[{"cat", "A"}, {"cat", "B"}, {"cat", "C"}, {"dog", "C"}, {"dog", "D"}]
Basically creating the combinations between item and keywords and removing duplicates.
Is that possible?
Thanks
You have to use $unwind on array and then you can use $group (by constant value) to get all elements into one array and $addToSet will handle uniqueness of specified pairs:
db.col.aggregate([
{
$unwind: "$keywords"
},
{
$group: {
_id: null,
unique: { $addToSet: { item: "$item", keyword: "$keywords" } }
}
}
])
You can then use onother $unwind on unique field to get a list of documents instead of single document as a result.
I need a Mongo Query to return me common values present in an array.
So if there are 4 documents in match, then the values are returned if those are present in in all the 4 documents
Suppose I have the below documents in my db
Mongo Documents
{
"id":"0",
"merchants":["1","2"]
}
{
"id":"1",
"merchants":["1","2","4"]
}
{
"id":"2",
"merchants":["4","5"]
}
Input : List of id
(i) Input with id "0" and "1"
Then it should return me merchants:["1","2"] as both are present in documents with id "0" & id "1"
(ii) Input with id "1" and "2"
Then it should return me merchants:["4"] as it is common and present in both documents with id "1" & id "2"
(iii) Input with id "0" and "2"
Should return empty merchants:[] as no common merchants between these 2 documents
You can try below aggregation.
db.collection.aggregate(
{$match:{id: {$in: ["1", "2"]}}},
{$group:{_id:null, first:{$first:"$merchants"}, second:{$last:"$merchants"}}},
{$project: {commonToBoth: {$setIntersection: ["$first", "$second"]}, _id: 0 } }
)
Say you have a function query that does the required DB query for you, and you'll call that function with idsToMatch which is an array containing all the elements you want to match. I have used JS here as the driver language, replace it with whatever you are using.
The following code is dynamic, will work for any number of ids you give as input:
const query = (idsToMatch) => {
db.collectionName.aggregate([
{ $match: { id: {$in: idsToMatch} } },
{ $unwind: "$merchants" },
{ $group: { _id: { id: "$id", data: "$merchants" } } },
{ $group: { _id: "$_id.data", count: {$sum: 1} } },
{ $match: { count: { $gte: idsToMatch.length } } },
{ $group: { _id: 0, result: {$push: "$_id" } } },
{ $project: { _id: 0, result: "$result" } }
])
The first $group statement is to make sure you don't have any
repetitions in any of your merchants attribute in a document. If
you are certain that in your individual documents you won't have any
repeated value for merchants, you need not include it.
The real work happens only upto the 2nd $match phase. The last two
phases ($group and $project) are only to prettify the result,
you may choose not use them, and instead use the language of your
choice to transform it in the form you want
Assuming you want to reduce the phases as per the points given above, the actual code will reduce to:
aggregate([
{ $match: { id: {$in: idsToMatch} } },
{ $unwind: "$merchants" },
{ $group: { _id: "merchants", count: {$sum: 1} } },
{ $match: { count: { $gte: idsToMatch.length } } }
])
Your required values will be at the _id attribute of each element of the result array.
The answer provided by #jgr0 is correct to some extent. The only mistake is the intermediate match operation
(i) So if input ids are "1" & "0" then the query becomes
aggregate([
{"$match":{"id":{"$in":["1","0"]}}},
{"$unwind":"$merchants"},
{"$group":{"_id":"$merchants","count":{"$sum":1}}},
{"$match":{"count":{"$eq":2}}},
{"$group":{"_id":null,"merchants":{"$push":"$_id"}}},
{"$project":{"_id":0,"merchants":1}}
])
(ii) So if input ids are "1", "0" & "2" then the query becomes
aggregate([
{"$match":{"id":{"$in":["1","0", "2"]}}},
{"$unwind":"$merchants"},
{"$group":{"_id":"$merchants","count":{"$sum":1}}},
{"$match":{"count":{"$eq":3}}},
{"$group":{"_id":null,"merchants":{"$push":"$_id"}}},
{"$project":{"_id":0,"merchants":1}}
])
The intermediate match operation should be the count of ids in input. So in case (i) it is 2 and in case (2) it is 3.
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.
Here is array structure
contact: {
phone: [
{
number: "+1786543589455",
place: "New Jersey",
createdAt: ""
}
{
number: "+1986543589455",
place: "Houston",
createdAt: ""
}
]
}
Here I only know the mongo id(_id) and phone number(+1786543589455) and I need to remove that whole corresponding array element from document. i.e zero indexed element in phone array is matched with phone number and need to remove the corresponding array element.
contact: {
phone: [
{
number: "+1986543589455",
place: "Houston",
createdAt: ""
}
]
}
I tried with following update method
collection.update(
{ _id: id, 'contact.phone': '+1786543589455' },
{ $unset: { 'contact.phone.$.number': '+1786543589455'} }
);
But it removes number: +1786543589455 from inner array object, not zero indexed element in phone array. Tried with pull also without a success.
How to remove the array element in mongodb?
Try the following query:
collection.update(
{ _id: id },
{ $pull: { 'contact.phone': { number: '+1786543589455' } } }
);
It will find document with the given _id and remove the phone +1786543589455 from its contact.phone array.
You can use $unset to unset the value in the array (set it to null), but not to remove it completely.
You can simply use $pull to remove a sub-document.
The $pull operator removes from an existing array all instances of a value or values that match a specified condition.
Collection.update({
_id: parentDocumentId
}, {
$pull: {
subDocument: {
_id: SubDocumentId
}
}
});
This will find your parent document against given ID and then will remove the element from subDocument which matched the given criteria.
Read more about pull here.
In Mongoose:
from the document:
To remove a document from a subdocument array we may pass an object
with a matching _id.
contact.phone.pull({ _id: itemId }) // remove
contact.phone.pull(itemId); // this also works
See Leonid Beschastny's answer for the correct answer.
To remove all array elements irrespective of any given id, use this:
collection.update(
{ },
{ $pull: { 'contact.phone': { number: '+1786543589455' } } }
);
To remove all matching array elements from a specific document:
collection.update(
{ _id: id },
{ $pull: { 'contact.phone': { number: '+1786543589455' } } }
);
To remove all matching array elements from all documents:
collection.updateMany(
{ },
{ $pull: { 'contact.phone': { number: '+1786543589455' } } }
);
Given the following document in the profiles collection:
{ _id: 1, votes: [ 3, 5, 6, 7, 7, 8 ] }
The following operation will remove all items from the votes array that are greater than or equal to ($gte) 6:
db.profiles.update( { _id: 1 }, { $pull: { votes: { $gte: 6 } } } )
After the update operation, the document only has values less than 6:
{ _id: 1, votes: [ 3, 5 ] }
If you multiple items the same value, you should use $pullAll instead of $pull.
In the question having a multiple contact numbers the same use this:
collection.update(
{ _id: id },
{ $pullAll: { 'contact.phone': { number: '+1786543589455' } } }
);
it will delete every item that matches that number. in contact phone
Try reading the manual.