Related
In MongoDB, is it possible to update the value of a field using the value from another field? The equivalent SQL would be something like:
UPDATE Person SET Name = FirstName + ' ' + LastName
And the MongoDB pseudo-code would be:
db.person.update( {}, { $set : { name : firstName + ' ' + lastName } );
The best way to do this is in version 4.2+ which allows using the aggregation pipeline in the update document and the updateOne, updateMany, or update(deprecated in most if not all languages drivers) collection methods.
MongoDB 4.2+
Version 4.2 also introduced the $set pipeline stage operator, which is an alias for $addFields. I will use $set here as it maps with what we are trying to achieve.
db.collection.<update method>(
{},
[
{"$set": {"name": { "$concat": ["$firstName", " ", "$lastName"]}}}
]
)
Note that square brackets in the second argument to the method specify an aggregation pipeline instead of a plain update document because using a simple document will not work correctly.
MongoDB 3.4+
In 3.4+, you can use $addFields and the $out aggregation pipeline operators.
db.collection.aggregate(
[
{ "$addFields": {
"name": { "$concat": [ "$firstName", " ", "$lastName" ] }
}},
{ "$out": <output collection name> }
]
)
Note that this does not update your collection but instead replaces the existing collection or creates a new one. Also, for update operations that require "typecasting", you will need client-side processing, and depending on the operation, you may need to use the find() method instead of the .aggreate() method.
MongoDB 3.2 and 3.0
The way we do this is by $projecting our documents and using the $concat string aggregation operator to return the concatenated string.
You then iterate the cursor and use the $set update operator to add the new field to your documents using bulk operations for maximum efficiency.
Aggregation query:
var cursor = db.collection.aggregate([
{ "$project": {
"name": { "$concat": [ "$firstName", " ", "$lastName" ] }
}}
])
MongoDB 3.2 or newer
You need to use the bulkWrite method.
var requests = [];
cursor.forEach(document => {
requests.push( {
'updateOne': {
'filter': { '_id': document._id },
'update': { '$set': { 'name': document.name } }
}
});
if (requests.length === 500) {
//Execute per 500 operations and re-init
db.collection.bulkWrite(requests);
requests = [];
}
});
if(requests.length > 0) {
db.collection.bulkWrite(requests);
}
MongoDB 2.6 and 3.0
From this version, you need to use the now deprecated Bulk API and its associated methods.
var bulk = db.collection.initializeUnorderedBulkOp();
var count = 0;
cursor.snapshot().forEach(function(document) {
bulk.find({ '_id': document._id }).updateOne( {
'$set': { 'name': document.name }
});
count++;
if(count%500 === 0) {
// Excecute per 500 operations and re-init
bulk.execute();
bulk = db.collection.initializeUnorderedBulkOp();
}
})
// clean up queues
if(count > 0) {
bulk.execute();
}
MongoDB 2.4
cursor["result"].forEach(function(document) {
db.collection.update(
{ "_id": document._id },
{ "$set": { "name": document.name } }
);
})
You should iterate through. For your specific case:
db.person.find().snapshot().forEach(
function (elem) {
db.person.update(
{
_id: elem._id
},
{
$set: {
name: elem.firstname + ' ' + elem.lastname
}
}
);
}
);
Apparently there is a way to do this efficiently since MongoDB 3.4, see styvane's answer.
Obsolete answer below
You cannot refer to the document itself in an update (yet). You'll need to iterate through the documents and update each document using a function. See this answer for an example, or this one for server-side eval().
For a database with high activity, you may run into issues where your updates affect actively changing records and for this reason I recommend using snapshot()
db.person.find().snapshot().forEach( function (hombre) {
hombre.name = hombre.firstName + ' ' + hombre.lastName;
db.person.save(hombre);
});
http://docs.mongodb.org/manual/reference/method/cursor.snapshot/
Starting Mongo 4.2, db.collection.update() can accept an aggregation pipeline, finally allowing the update/creation of a field based on another field:
// { firstName: "Hello", lastName: "World" }
db.collection.updateMany(
{},
[{ $set: { name: { $concat: [ "$firstName", " ", "$lastName" ] } } }]
)
// { "firstName" : "Hello", "lastName" : "World", "name" : "Hello World" }
The first part {} is the match query, filtering which documents to update (in our case all documents).
The second part [{ $set: { name: { ... } }] is the update aggregation pipeline (note the squared brackets signifying the use of an aggregation pipeline). $set is a new aggregation operator and an alias of $addFields.
Regarding this answer, the snapshot function is deprecated in version 3.6, according to this update. So, on version 3.6 and above, it is possible to perform the operation this way:
db.person.find().forEach(
function (elem) {
db.person.update(
{
_id: elem._id
},
{
$set: {
name: elem.firstname + ' ' + elem.lastname
}
}
);
}
);
I tried the above solution but I found it unsuitable for large amounts of data. I then discovered the stream feature:
MongoClient.connect("...", function(err, db){
var c = db.collection('yourCollection');
var s = c.find({/* your query */}).stream();
s.on('data', function(doc){
c.update({_id: doc._id}, {$set: {name : doc.firstName + ' ' + doc.lastName}}, function(err, result) { /* result == true? */} }
});
s.on('end', function(){
// stream can end before all your updates do if you have a lot
})
})
update() method takes aggregation pipeline as parameter like
db.collection_name.update(
{
// Query
},
[
// Aggregation pipeline
{ "$set": { "id": "$_id" } }
],
{
// Options
"multi": true // false when a single doc has to be updated
}
)
The field can be set or unset with existing values using the aggregation pipeline.
Note: use $ with field name to specify the field which has to be read.
Here's what we came up with for copying one field to another for ~150_000 records. It took about 6 minutes, but is still significantly less resource intensive than it would have been to instantiate and iterate over the same number of ruby objects.
js_query = %({
$or : [
{
'settings.mobile_notifications' : { $exists : false },
'settings.mobile_admin_notifications' : { $exists : false }
}
]
})
js_for_each = %(function(user) {
if (!user.settings.hasOwnProperty('mobile_notifications')) {
user.settings.mobile_notifications = user.settings.email_notifications;
}
if (!user.settings.hasOwnProperty('mobile_admin_notifications')) {
user.settings.mobile_admin_notifications = user.settings.email_admin_notifications;
}
db.users.save(user);
})
js = "db.users.find(#{js_query}).forEach(#{js_for_each});"
Mongoid::Sessions.default.command('$eval' => js)
With MongoDB version 4.2+, updates are more flexible as it allows the use of aggregation pipeline in its update, updateOne and updateMany. You can now transform your documents using the aggregation operators then update without the need to explicity state the $set command (instead we use $replaceRoot: {newRoot: "$$ROOT"})
Here we use the aggregate query to extract the timestamp from MongoDB's ObjectID "_id" field and update the documents (I am not an expert in SQL but I think SQL does not provide any auto generated ObjectID that has timestamp to it, you would have to automatically create that date)
var collection = "person"
agg_query = [
{
"$addFields" : {
"_last_updated" : {
"$toDate" : "$_id"
}
}
},
{
$replaceRoot: {
newRoot: "$$ROOT"
}
}
]
db.getCollection(collection).updateMany({}, agg_query, {upsert: true})
(I would have posted this as a comment, but couldn't)
For anyone who lands here trying to update one field using another in the document with the c# driver...
I could not figure out how to use any of the UpdateXXX methods and their associated overloads since they take an UpdateDefinition as an argument.
// we want to set Prop1 to Prop2
class Foo { public string Prop1 { get; set; } public string Prop2 { get; set;} }
void Test()
{
var update = new UpdateDefinitionBuilder<Foo>();
update.Set(x => x.Prop1, <new value; no way to get a hold of the object that I can find>)
}
As a workaround, I found that you can use the RunCommand method on an IMongoDatabase (https://docs.mongodb.com/manual/reference/command/update/#dbcmd.update).
var command = new BsonDocument
{
{ "update", "CollectionToUpdate" },
{ "updates", new BsonArray
{
new BsonDocument
{
// Any filter; here the check is if Prop1 does not exist
{ "q", new BsonDocument{ ["Prop1"] = new BsonDocument("$exists", false) }},
// set it to the value of Prop2
{ "u", new BsonArray { new BsonDocument { ["$set"] = new BsonDocument("Prop1", "$Prop2") }}},
{ "multi", true }
}
}
}
};
database.RunCommand<BsonDocument>(command);
MongoDB 4.2+ Golang
result, err := collection.UpdateMany(ctx, bson.M{},
mongo.Pipeline{
bson.D{{"$set",
bson.M{"name": bson.M{"$concat": []string{"$lastName", " ", "$firstName"}}}
}},
)
I have a query where I first want to match find the list of matched users and then filter the matches out from the array of external users that was passed in so that I am left with users Id's that have not been matched yet.
Here is a the match Schema:
const mongoose = require('mongoose'); // only match two users at a time.
const Schema = mongoose.Schema;
const MatchSchema = new Schema({
participants: [{
type: String, ref: 'user'
}],
blocked: {
type: Boolean,
default: false
}
});
Here is the query with explanations:
db.getCollection('match').aggregate([
{
'$match': {
'$and': [
{ participants: "599f14855e9fcf95d0fe11a7" }, // the current user.
{ participants: {'$in': [ "598461fcda5afa9e0d2a8a64","598461fcda5afa9e0d111111", "599f14855e9fcf95d0fe5555"] } } // array of external users that I want to check if the current user is matched with.
]
}
},
{
'$project': {
'participants': 1
}
},
This returns the following result:
{
"_id" : ObjectId("59c0d76e66dd407f5efe7112"),
"participants" : [
"599f14855e9fcf95d0fe11a7",
"599f14855e9fcf95d0fe5555"
]
},
{
"_id" : ObjectId("59c0d76e66dd407f5efe75ac"),
"participants" : [
"598461fcda5afa9e0d2a8a64",
"599f14855e9fcf95d0fe11a7"
]
}
what I want to do next it merge the participants array form both results into one array.
Then I want to take away the those matching items from the array of external users so that I am left with user id's that have not been matched yet.
Any help would be much appreciated!
If you don't want those results in the array, then $filter them out.
Either by building the conditions with $or ( aggregation logical version ):
var currentUser = "599f14855e9fcf95d0fe11a7",
matchingUsers = [
"598461fcda5afa9e0d2a8a64",
"598461fcda5afa9e0d111111",
"599f14855e9fcf95d0fe5555"
],
combined = [currentUser, ...matchingUsers];
db.getCollection('match').aggregate([
{ '$match': {
'participants': { '$eq': currentUser, '$in': matchingUsers }
}},
{ '$project': {
'participants': {
'$filter': {
'input': '$participants',
'as': 'p',
'cond': {
'$not': {
'$or': combined.map(c =>({ '$eq': [ c, '$$p' ] }))
}
}
}
}
}}
])
Or use $in ( again the aggregation version ) if you have MongoDB 3.4 which supports it:
db.getCollection('match').aggregate([
{ '$match': {
'participants': { '$eq': currentUser, '$in': matchingUsers }
}},
{ '$project': {
'participants': {
'$filter': {
'input': '$participants',
'as': 'p',
'cond': {
'$not': {
'$in': ['$p', combined ]
}
}
}
}
}}
])
It really does not matter. It's just the difference of using JavaScript to build the expression before the pipeline is sent or letting a supported pipeline operator do the array comparison where it is actually supported.
Note you can also write the $match a bit more efficiently by using an "implicit" form of $and, as is shown.
Also note you have a problem in your schema definition ( but not related to this particular query ). You cannot use a "ref" to another collection as String in one collection where it is going to be ObjectId ( the default for _id, and presumed of the hex values obtained ) in the other. This mismatch means .populate() or $lookup functions cannot work. So you really should correct the types.
Unrelated to this. But something you need to fix as a priority.
I know that MongoDB supports the syntax find{array.0.field:"value"}, but I specifically want to do this for the last element in the array, which means I don't know the index. Is there some kind of operator for this, or am I out of luck?
EDIT: To clarify, I want find() to only return documents where a field in the last element of an array matches a specific value.
In 3.2 this is possible. First project so that myField contains only the last element, and then match on myField.
db.collection.aggregate([
{ $project: { id: 1, myField: { $slice: [ "$myField", -1 ] } } },
{ $match: { myField: "myValue" } }
]);
You can use $expr ( 3.6 mongo version operator ) to use aggregation functions in regular query.
Compare query operators vs aggregation comparison operators.
For scalar arrays
db.col.find({$expr: {$gt: [{$arrayElemAt: ["$array", -1]}, value]}})
For embedded arrays - Use $arrayElemAt expression with dot notation to project last element.
db.col.find({$expr: {$gt: [{"$arrayElemAt": ["$array.field", -1]}, value]}})
Spring #Query code
#Query("{$expr:{$gt:[{$arrayElemAt:[\"$array\", -1]}, ?0]}}")
ReturnType MethodName(ArgType arg);
Starting Mongo 4.4, the aggregation operator $last can be used to access the last element of an array:
For instance, within a find query:
// { "myArray": ["A", "B", "C"] }
// { "myArray": ["D"] }
db.collection.find({ $expr: { $eq: [{ $last: "$myArray" }, "C"] } })
// { "myArray": ["A", "B", "C"] }
Or within an aggregation query:
db.collection.aggregate([
{ $addFields: { last: { $last: "$myArray" } } },
{ $match: { last: "C" } }
])
use $slice.
db.collection.find( {}, { array_field: { $slice: -1 } } )
Editing:
You can make use of
{ <field>: { $elemMatch: { <query1>, <query2>, ... } } } to find a match.
But it won't give exactly what you are looking for. I don't think that is possible in mongoDB yet.
I posted on the official Mongo Google group here, and got an answer from their staff. It appears that what I'm looking for isn't possible. I'm going to just use a different schema approach.
Version 3.6 use aggregation to achieve the same.
db.getCollection('deviceTrackerHistory').aggregate([
{
$match:{clientId:"12"}
},
{
$project:
{
deviceId:1,
recent: { $arrayElemAt: [ "$history", -1 ] }
}
}
])
You could use $position: 0 whenever you $push, and then always query array.0 to get the most recently added element. Of course then, you wont be able to get the new "last" element.
Not sure about performance, but this works well for me:
db.getCollection('test').find(
{
$where: "this.someArray[this.someArray.length - 1] === 'pattern'"
}
)
You can solve this using aggregation.
model.aggregate([
{
$addFields: {
lastArrayElement: {
$slice: ["$array", -1],
},
},
},
{
$match: {
"lastArrayElement.field": value,
},
},
]);
Quick explanations. aggregate creates a pipeline of actions, executed sequentially, which is why it takes an array as parameter. First we use the $addFields pipeline stage. This is new in version 3.4, and basically means: Keep all the existing fields of the document, but also add the following. In our case we're adding lastArrayElement and defining it as the last element in the array called array. Next we perform a $match pipeline stage. The input to this is the output from the previous stage, which includes our new lastArrayElement field. Here we're saying that we only include documents where its field field has the value value.
Note that the resulting matching documents will include lastArrayElement. If for some reason you really don't want this, you could add a $project pipeline stage after $match to remove it.
For the answer use $arrayElemAt,if i want orderNumber:"12345" and the last element's value $gt than "value"? how to make the $expr? thanks！
For embedded arrays - Use $arrayElemAt expression with dot notation to project last element.
db.col.find({$expr: {$gt: [{"$arrayElemAt": ["$array.field", -1]}, value]}})
db.collection.aggregate([
{
$match: {
$and: [
{ $expr: { $eq: [{ "$arrayElemAt": ["$fieldArray.name", -1] }, "value"] } },
{ $or: [] }
]
}
}
]);
I've stumbled upon some very strange behavior with MongoDB. For my test case, I have an MongoDB collection with 9 documents. All documents have the exact same structure, including the fields expired_at: Date and location: [lng, lat].
I now need to find all documents that are not expired yet and are within a bounding box; I show match documents on map. for this I set up the following queries:
var qExpiry = {"expired_at": { $gt : new Date() } };
var qLocation = { "location" : { $geoWithin : { $box : [ [ 123.8766, 8.3269 ] , [ 122.8122, 8.24974 ] ] } } };
var qFull = { $and: [ qExpiry, qLocation ] };
Since the expiry date is long in the past, and when I set the bounding box large enough, the following queries give me all 9 documents as expected:
db.docs.find(qExpiry);
db.docs.find(qLocation);
db.docs.find(qFull);
db.docs.find(qExpiry).sort({"created_at" : -1});
db.docs.find(qLocation).sort({"created_at" : -1});
Now here's the deal: The following query returns 0 documents:
db.docs.find(qFull).sort({"created_at" : -1});
Just adding sort to the AND query ruins the result (please note that I want to sort since I also have a limit in order to avoid cluttering the map on larger scales). Sorting by other fields yield the same empty result. What's going on here?
(Actually even stranger: When I zoom into my map, I sometimes get results for qFull, even with sorting. One could argue that qLocation is faulty. But when I only use qLocation, the results are always correct. And qExpiry is always true for all documents anyway)
You may want to try running the same query using the aggregation framework's $match and $sort pipelines:
db.docs.aggregate([
{ "$match": qFull },
{ "$sort": { "created_at": -1 } }
]);
or implicitly using $and by specifiying a comma-separated list of expressions as in
db.docs.aggregate([
{
"$match": {
"expired_at": { "$gt" : new Date() },
"location" : {
"$geoWithin" : {
"$box" : [
[ 123.8766, 8.3269 ],
[ 122.8122, 8.24974 ]
]
}
}
}
},
{ "$sort": { "created_at": -1 } }
]);
Not really sure why that fails with find()
chridam suggestion using the aggregation framework of MongoDB proved to be the way to go. My working query now looks like this:
db.docs.aggregate(
[
{ $match : { $and : [qExpiry, qLocation]} },
{ $sort: {"created_at": -1} }.
{ $limit: 50 }.
]
);
Nevertheless, if any can point out way my first approach did not work, that would be very useful. Simply adding sort() to a non-empty query shouldn't suddenly return 0 documents. Just to add, since I still tried for a bit, .sort({}) return all documents but was not very useful. Everything else failed including .sort({'_id': 1}).
This question already has an answer here:
Combine two OR-queries with AND in Mongoose
(1 answer)
Closed 8 years ago.
I want to query mongo for "unexpired or evergreen(posts with null expiration) posts created or bookmarked by me"
The problem with my query is that mongoose is combining the or statements together so that I'm incorrectly getting (unexpired or evergreen or mine or bookmarked) rather than ( (unexpired or evergreen) and (mine or bookmarked) )
How do I change the mongoose query to be the latter correct case I outlined above. Should I use an "and" clause... or perhaps I should just do a not(expiration > now) ?
var query =
Invite.find({ isActive:true })
.or([
{ 'expiration': {$gt: new Date()} },
{ 'expiration' : null }
])
.or([
{ createdBy:userId },
{ 'bookmarked.id' : userId }
])
You can put both of the $or clauses into a single $and by using the Query#and helper as:
var query =
Invite.find({ isActive:true })
.and([
{$or: [
{ 'expiration': {$gt: new Date()} },
{ 'expiration': null }
]},
{$or: [
{ 'createdBy': userId },
{ 'bookmarked.id' : userId }
]}
])
This is where I think "helper" methods are not really helping much because they are confusing the issue. JavaScript is a dynamically typed language so you don't need these helper methods to define the data structure which makes up the query. All the native operators to MongoDB are just accepted in the single query path:
Invite.find(
{
"isActive": true,
"$and": [
{ "$or": [
{ "expiration": null },
{ "expiration": { "$gt": new Date() } }
]},
{ "$or": [
{ "createdBy": userId }
{ "bookmarked.id": userId }
]}
]
},
function(err,result) {
}
);