I have a collection called student, now I want to update the object value inside array based on condition. Can anyone help me to figure this logic please.
Student:
{
_id: "5996d10e0b992e5def651db4"
name: "Siva"
mark:[
{subject:"Tamil",mark:"50"},
{subject:"English",mark:"25"},
{subject:"Science",mark:"25"},
]
__v: 36
}
Expected Result:
I want to update only Tamil mark by checking the subject value...
You can update sub-array element or object by using positional operator $, in your example it should something like this:
Student.update(
{ "mark.subject": "Tamil" },
{ "$set": { "mark.$.mark": "60" } }
)
You can read more documentation here
Related
Use case
Adding a field to a specific object in an array of objects using updateOne during a bulkUpdateOps
Blockers
I have been unable to find a way to identify and update a specific object in the subdocument array of a specific record.
I only have access to this DB through MongoDB Compass, and I plan to use the provided mongosh tool.
Data example
Our purchaseorders model looks like this:
{
_id: uuid,
...rest,
documents:[
{
_id:uuid,
forignKey2:string (optional),
keyIWantToAdd:string (optional),
...rest
}
]
}
So if I have
{
_id:*1,
documents:[
{
_id:*2,
forignKey2:'no-test',
...rest
},
{
_id:*3,
forignKey2:'test',
...rest
},
]
}
I want to add a key and value like this (really I'm willing to do anything to set these values, this is just the closest I have been able to get):
var bulkUpdateOps = db.purchaseorders.initializeOrderedBulkOp();
bulkUpdateOps.find('*1').updateOne({
$set:{
documents.[index of document object with forignKey2:'test' or _id:*3 whichever is easier].keyIWantToAdd:'valueIWantToAdd'
}
})
bulkUpdateOps.execute();
Any help or suggestions would be greatly appreciated.
#rickhg12hs posted exactly what I was looking for. For anyone else using mongodb.com/docs/manual/reference/method/Bulk.find.arrayFilters the bulk find is being ran on an array of objects like this: { grades:[ { grade: 85, mean: number } ] }
I'm trying to update an array that sits inside another array in a document. The schema is like this:
const projectSchema = new mongoose.Schema({
stakeholders: [{
stakeholderTitle: {
type: String,
},
...
subgroup: [{
subgroupTitle: {
type: String
},
subgroupPercent: {
type: Number,
}
}]
}],
and I'm trying to update the 'subgroup' array. I have got the query to work on its parent (the stakeholder array) with the positional $ operator, using the answer to this question I asked previously. So my query looks like this.....
await db.findOneAndUpdate({ find by the id }, { "stakeholders.$.stakeholderTitle": req.body.stakeholderTitle, ... "stakeholders.$.subgroup": req.body.subgroup })
However, this query doesn't work for the 'stakeholders subgroup' array, and makes it null. Looking through the mongo docs for the positional operator it states that 'The positional $ operator cannot be used for queries which traverse more than one array, such as queries that traverse arrays nested within other arrays, because the replacement for the $ placeholder is a single value', which I guess might be my problem.
So how can I do this with a findOneAndUpdate query?
From what I see is you have to specify the object you want to update inside the subgroup array. Try this - (i.e I'm updating the subgroupTitle of the subgroup array);
await db.findOneAndUpdate(
{
_id: userId,
"stakeholders.stakeholderTitle": req.body.stakeholderTitle,
"stakeholders.stakeholderTitle.subgroup.subgroupTitle": req.body.subgroupTitle
},
{$set: {
"stakeholders.stakeholderTitle.subgroup.$.subgroupPercent": somePercentValue,
}
},
);
Also note, it's only the array that you find that you can update. It might not be exactly what you want, but its a step closer
I have the data like below:
{
info:{
id:0000,
name:"Iot name",
vendor:"some vendor",
},
location:[
{
lat:0,
lng:0,
status:3,
locID:"uniqueID0"
},{
lat:1,
lng:1,
status:0,
locID:"uniqueID1"
},{
lat:2,
lng:2,
status:1,
locID:"uniqueID2"
}
]}
Need example like findAndModify or something else similar, to find
in the iots collection, location with a unique ID and change his status.
e.g Find in collection iot, element with id=0000 and location with locID="uniqueID1" and set status for that location into 2
Thanks in advance
Apply the $set operator together with the $ positional operator in your update to change set the status field for that location to 2. The $ positional operator will identify the correct element in the array to update without explicitly specifying the position of the element in the array, thus your final update statement should look like:
db.iost.update(
{
"info.id": 0000,
"location.locID": "uniqueID1"
},
{
"$set": {
"location.$.status": 2
}
}
)
I would like to mark all messages as read by 'jim'. Here is the structure of a thread:
db.threads.save({
messages: [
{
read_by: ['bob', 'jim']
},
{
read_by: ['bob']
},
{
read_by: ['bob']
}
]
})
As you can see, one message has already been read by 'jim', the rest only by 'bob'. I'd like to find and modify any embedded documents so that 'jim' is appended to the read_by array.
Here is where I got:
db.threads.findAndModify({
query: {
'messages.read_by': {
$ne: 'jim'
}
},
update: {
$push: {
'messages.$.read_by': 'jim'
}
}
})
I get this error:
uncaught exception: findAndModifyFailed failed: "can't append to array using string field name [$]"
The query works with a db.threads.find() so I guess the problem is with the update part of the findAndModify() call.
I know its been a while, but pushes into nested documents is indeed possible. You need to add an each into it. For example,
db.threads.update({
'messages.read_by': {
$ne: 'jim'
}
},
{
$push: {
'messages.read_by': {
$each: ['jim']
}
}
}
)
See here for more samples - http://docs.mongodb.org/manual/reference/operator/update/push/
Even though you are just passing only one value, for nested arrays, you need to pass $each. If the document already contains a read_by field with some values in it, then an update without the each works. Using the $each will work irrespective of whether the field exists or not.
With one operation, you can't do this yet. See this question, which is the same as yours.
You will have to this sort of operation in your application: find() all messages which jim has not already read, append him to them, and then set the messages field of your thread to this array.
In the MongoDB aggregation framework, I was hoping to use the $unwind operator on an object (ie. a JSON collection). Doesn't look like this is possible, is there a workaround? Are there plans to implement this?
For example, take the article collection from the aggregation documentation . Suppose there is an additional field "ratings" that is a map from user -> rating. Could you calculate the average rating for each user?
Other than this, I'm quite pleased with the aggregation framework.
Update: here's a simplified version of my JSON collection per request. I'm storing genomic data. I can't really make genotypes an array, because the most common lookup is to get the genotype for a random person.
variants: [
{
name: 'variant1',
genotypes: {
person1: 2,
person2: 5,
person3: 7,
}
},
{
name: 'variant2',
genotypes: {
person1: 3,
person2: 3,
person3: 2,
}
}
]
It is not possible to do the type of computation you are describing with the aggregation framework - and it's not because there is no $unwind method for non-arrays. Even if the person:value objects were documents in an array, $unwind would not help.
The "group by" functionality (whether in MongoDB or in any relational database) is done on the value of a field or column. We group by value of field and sum/average/etc based on the value of another field.
Simple example is a variant of what you suggest, ratings field added to the example article collection, but not as a map from user to rating but as an array like this:
{ title : title of article", ...
ratings: [
{ voter: "user1", score: 5 },
{ voter: "user2", score: 8 },
{ voter: "user3", score: 7 }
]
}
Now you can aggregate this with:
[ {$unwind: "$ratings"},
{$group : {_id : "$ratings.voter", averageScore: {$avg:"$ratings.score"} } }
]
But this example structured as you describe it would look like this:
{ title : title of article", ...
ratings: {
user1: 5,
user2: 8,
user3: 7
}
}
or even this:
{ title : title of article", ...
ratings: [
{ user1: 5 },
{ user2: 8 },
{ user3: 7 }
]
}
Even if you could $unwind this, there is nothing to aggregate on here. Unless you know the complete list of all possible keys (users) you cannot do much with this. [*]
An analogous relational DB schema to what you have would be:
CREATE TABLE T (
user1: integer,
user2: integer,
user3: integer
...
);
That's not what would be done, instead we would do this:
CREATE TABLE T (
username: varchar(32),
score: integer
);
and now we aggregate using SQL:
select username, avg(score) from T group by username;
There is an enhancement request for MongoDB that may allow you to do this in the aggregation framework in the future - the ability to project values to keys to vice versa. Meanwhile, there is always map/reduce.
[*] There is a complicated way to do this if you know all unique keys (you can find all unique keys with a method similar to this) but if you know all the keys you may as well just run a sequence of queries of the form db.articles.find({"ratings.user1":{$exists:true}},{_id:0,"ratings.user1":1}) for each userX which will return all their ratings and you can sum and average them simply enough rather than do a very complex projection the aggregation framework would require.
Since 3.4.4, you can transform object to array using $objectToArray
See:
https://docs.mongodb.com/manual/reference/operator/aggregation/objectToArray/
This is an old question, but I've run across a tidbit of information through trial and error that people may find useful.
It's actually possible to unwind on a dummy value by fooling the parser this way:
db.Opportunity.aggregate(
{ $project: {
Field1: 1, Field2: 1, Field3: 1,
DummyUnwindField: { $ifNull: [null, [1.0]] }
}
},
{ $unwind: "$DummyUnwindField" }
);
This will produce 1 row per document, regardless of whether or not the value exists. You may be able tinker with this to generate the results you want. I had hoped to combine this with multiple $unwinds to (sort of like emit() in map/reduce), but alas, the last $unwind wins or they combine as an intersection rather than union which makes it impossible to achieve the results I was looking for. I am sadly disappointed with the aggregate framework functionality as it doesn't fit the one use case I was hoping to use it for (and seems strangely like a lot of the questions on StackOverflow in this area are asking) - ordering results based on match rate. Improving the poor map reduce performance would have made this entire feature unnecessary.
This is what I found & extended.
Lets create experimental database in mongo
db.copyDatabase('livedb' , 'experimentdb')
Now Use experimentdb & convert Array to object in your experimentcollection
db.getCollection('experimentcollection').find({}).forEach(function(e){
if(e.store){
e.ratings = [e.ratings]; //Objects name to be converted to array eg:ratings
db.experimentcollection.save(e);
}
})
Some nerdy js code to convert json to flat object
var flatArray = [];
var data = db.experimentcollection.find().toArray();
for (var index = 0; index < data.length; index++) {
var flatObject = {};
for (var prop in data[index]) {
var value = data[index][prop];
if (Array.isArray(value) && prop === 'ratings') {
for (var i = 0; i < value.length; i++) {
for (var inProp in value[i]) {
flatObject[inProp] = value[i][inProp];
}
}
}else{
flatObject[prop] = value;
}
}
flatArray.push(flatObject);
}
printjson(flatArray);