I have a document like this:
{
project: 'Book',
author: 'Author',
pages: [{},{},{},{}]
}
for example I want to remove second element from pages array. I try to do something like this:
db.t.update(_id: "53296f43630a817c1af2a3e8"}, {$pull:{'test.$':1}})
but it isn't work for me.
Well the way you put it, it's going to be hard to match because there is nothing in there. But in the real world you would probably try to match like this:
db.t.update(
{ "_id": "53296f43630a817c1af2a3e8" },
{ "$pull": { "pages": { "value": 1 } }
)
That is assuming that there is a "value" property in the "sub-document".
But if you really do mean something like this where the is nothing to match, then try this:
db.t.update(
{ "_id": "53296f43630a817c1af2a3e8" },
{ "$set": { "pages.1": false } }
);
db.t.update(
{ "_id": "53296f43630a817c1af2a3e8" },
{ "$pull": { "pages": false } }
)
Which sets a value you can match and then matches and removes it.
Related
Got multiple documents in a db one of which looks like this:
{
"searchWord":[
"pizz",
"pizza"
],
"result":[
{
"idMeal":1,
"strMeal":"test1",
"strInstructions":"test1"
},
{
"idMeal":2,
"strMeal":"test2",
"strInstructions":"test2"
}
]
}
Tried to solve it like this:
eg:
db.meals.updateOne(
{
"searchWord": "pizz",
"result": { $elemMatch: { idMeal: "1" } }
},
{ $set: { 'result.$.strMeal' : "UPDATED" } }
)
This doesnt update the respective subdocument only the 2nd as if I wrote
{ $set: { 'result.1.strMeal' : "UPDATED" } }
(Which will result in the 2nd subdocument being updated)
This is the other idea (Same result)
db.meals.updateOne(
{ searchWord: "pizz", 'result.idMeal': 319012 },
{ $set: { "result.$.strMeal" : "fsdf" } }
)
What I dont seem to understand is its exactly the syntax that is provided by mongo yet it doesnt work
The "$" operator doesnt pick up which array of objects I wanna update
Try to use $[] in your $set for multiple positional element
db.collection.update({
"searchWord": "pizz"
},
{
$set: {
"result.$[r].strMeal": "UPDATED"
}
},
{
arrayFilters: [
{
"r.idMeal": 1
}
]
})
Here is the Mongo playground for your reference.
I currently have a problem where I have to update entries in a deeply nested Document. Now to simplify my problem I have this example. Let's assume I store cars in my MongoDB. A Document would look like this
{
Make: "BMW",
Model: "3Series",
Wheels: [
{
_id: someObjectId
Size: "19 inch",
Screws: [
{
_id: someObjectId
Type : "M15x40"
},
{
_id: someObjectId
Type : "M15x40"
}
]
}
]
}
Now if I want to update a specific Wheel, my code would look somewhat like this
CarModel.findOneAndUpdate({
"_id": CarId, "Wheels._id": WheelId
}, {
"$set" : {
"Wheels.$.Size": NewSize
}
})
Now this works. But I am pretty lost on how I would update an specific screw as I am going through 2 Arrays. Any Idea how I could make this work?
You need arrayFilters functionality to define the path for more than one nested array:
CarModel.findOneAndUpdate(
{ "_id": CarId },
{ $set: { "Wheels.$[wheel].Screws.$[screw].Type": "something" } },
{ arrayFilters: [ { 'wheel._id': WheelId }, { 'screw._id': screwId } ] })
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.
I have a document with the array of objects and one object contains multiple objects I want to update inner object with $set but didn't get any luck.
can anybody give me any hint so that I can resolve it?.
This is my object:
{
"_id": ObjectId("56fbfafdf86fa6161911d104"),
"site": "xyz",
"adsPerCategory": NumberInt(2),
"sampledAt": ISODate("2016-03-30T16:12:45.138+0000"),
"items": [
{
"id": "4563873",
"content": {
"title": "WATER DISTILLERS",
"body": "Perfect to save money.",
}
},
{
"id": "4563s23232873",
"content": {
"title": "Cola water",
"body": "Perfect for body.",
}
}
]
}
I want to update body.
for now, I have given single object but it can be multiple.
Here what I tried
models.Sample.update(
{
_id: samples._id
},
'$set': {
'items.0.content.body': body.description
},
function(err, numAffected) {
console.log(err);
console.log('Affected....', numAffected);
}
);
It's working fine if I put 0 but I want to make it dynamic.
Like 'items.index.content.body': body.description
Thank You.
I think you can do something like this.
models.Sample.find({ _id: ObjectId(samples._id) })
.forEach(function (doc) {
doc.items.forEach(function (element, index, array) {
items[index].content.body = body.description;
});
models.Sample.save(doc);
});
say I have this array property ('articles') on a Mongoose schema:
articles: [
{
kind: 'bear',
hashtag: 'foo'
},
{
kind: 'llama',
hashtag: 'baz',
},
{
kind: 'sheep',
hashtag: 'bar',
}
]
how can I use
$pull https://docs.mongodb.org/manual/reference/operator/update/pull/
to remote objects from this array by checking the value of hashtag to see if it matches a pattern?
For example, if I want to remove an object in the articles array where hashtag='foo'.
My best guess is the following, but it doesn't seem to work:
var data = {
"$pull": {
"articles": {
"$elemMatch": {
"hashtag": "foo"
}
}
}
};
Model.update({},data); //doesn't quite work
this one seems to work:
var data = {
"$pull": {
"articles": {
"hashtag": 'foo'
}
}
};
Model.update({},data); //seems to work
if you have a better solution or if you can show an alternate solution please provide an answer thank you
The $pull operator is basically a "mini query" in itself, and as such operators like $elemMatch become irrelevant as the "query" is directly performed on each array member anyway.
As such:
Model.update(
{},
{ "$pull": { "articles": { "hashtag": "foo" }},
{ "multi": true },
function(err,numAffected) {
// handle result here
}
)
So it is looking for the matching properties within the ( correct ) specified array in all array documents, and then removing them where there is a match.
The .update() also just returns the number of affected documents, and is usually used with { "multi": true } when you expect more than one document to be updated.
If you are just looking for "one" document, or expect the modified document in response, then use .findOneAndUpdate() instead:
Model.findOneAndUpdate(
{},
{ "$pull": { "articles": { "hashtag": "foo" }},
{ "new": true },
function(err,numAffected) {
// handle result here
}
)
Though not really practical without any selection criteria, since this just updates the first document found in the collection.