I use mongodb 4.0.5. I'm using lookup to join two collections, the foreign key is a string value located in request_by array and the other one is
ObjectId
{
$addFields: {
convertedId: {
$toObjectId: "$request_by.userId"
}
}
}
i want to convert the foreign key to ObjectId so i can join them. But it says "Unsupported conversion from array to objectId in $convert with no onError value"
i have a data something like this:
Simulation collection
{
"_id": "8f361e8969948e1c435c06d7",
"request_by": [{
"userId": "ae83ccfa592f4963a395263c",
"iat": 1544801930,
"exp": 1544819930
}],
"status": "finish",
"start": "2018-12-14T15:39:29.588Z",
"end": "2018-12-14T16:59:29.538Z",
"duration": 80,
"passing_grade": 100,
"created_at": "2018-12-14T15:39:29.588Z",
"updated_at": "2018-12-14T15:43:12.897Z",
"__v": 0
}
How i can join them if i have data like that?
You need $map since request_by is an array, then you can pass that array directly into $lookup (joins single fields or arrays).
{
$addFields: {
convertedId: {
$map: {
input: "$request_by",
as: "r",
in: { $toObjectId: "$$r.userId" }
}
}
}
}
Related
There is this weird thing,
I have installed the MongoDB Compass and made a aggregation query that works in the Aggregation tab but now when I use the same query in my rust web server it behaves very weirdly
Original message:
{"_id":{"$oid":"61efd41c56ffe6b1b4a15c7a"},"time":{"$date":"2022-01-25T10:42:36.175Z"},"edited_time":{"$date":"2022-01-30T14:29:54.361Z"},"changes":[],"content":"LORA","author":{"$oid":"61df3cab3087579f8767a38d"}}
Message in MongoDB compass after the query:
{
"_id": {
"$oid": "61efd41c56ffe6b1b4a15c7a"
},
"time": {
"$date": "2022-01-25T10:42:36.175Z"
},
"edited_time": {
"$date": "2021-12-17T09:55:45.856Z"
},
"changes": [{
"time": {
"$date": "2021-12-17T09:55:45.856Z"
},
"change": {
"ChangedContent": "LORA"
}
}],
"content": "LMAO",
"author": {
"$oid": "61df3cab3087579f8767a38d"
}
}
Message after the Web Servers query:
{
"_id": {
"$oid": "61efd41c56ffe6b1b4a15c7a"
},
"time": {
"$date": "2022-01-25T10:42:36.175Z"
},
"edited_time": {
"$date": "2022-01-30T14:40:57.152Z"
},
"changes": {
"$concatArrays": ["$changes", [{
"time": {
"$date": "2022-01-30T14:40:57.152Z"
},
"change": {
"ChangedContent": "$content"
}
}]]
},
"content": "LMAO",
"author": {
"$oid": "61df3cab3087579f8767a38d"
}
}
Pure query in MongoDB Compass:
$set stage
{
"changes": { $concatArrays: [ "$changes", [ { "time": ISODate('2021-12-17T09:55:45.856+00:00'), "change": { "ChangedContent": "$content" } } ] ] },
"edited_time": ISODate('2021-12-17T09:55:45.856+00:00'),
"content": "LMAO",
}
Pure query in Web Server:
let update_doc = doc! {
"$set": {
"changes": {
"$concatArrays": [
"$changes", [
{
"time": now,
"change": {
"ChangedContent": "$content"
}
}
]
]
},
"edited_time": now,
"content": content
}
};
I am using update_one method,
like this
messages.update_one(message_filter, update_doc, None).await?;
I don't really understand, and this happens often, sometimes it fixes it self when I add somewhere randomly some scope in the doc eg.: { } but this time I couldn't figure it out,
I had version of the query with $push but that didn't work too
Is there some fault in the rust driver or am I doing something wrong, are there some rules about formatting when using rust driver that I am missing?
The $set aggregation pipeline stage is different from the $set update operator. And the only difference that I can tell, is the pipeline stage handles $concatArrays while the update operator does not.
$set Aggregation Pipeline Stage
$set appends new fields to existing documents. You can include one or more $set stages in an aggregation operation.
To add field or fields to embedded documents (including documents in arrays) use the dot notation.
To add an element to an existing array field with $set, use with $concatArrays.
$set Update Operator
Starting in MongoDB 5.0, update operators process document fields with
string-based names in lexicographic order. Fields with numeric names
are processed in numeric order.
If the field does not exist, $set will add a new field with the
specified value, provided that the new field does not violate a type
constraint. If you specify a dotted path for a non-existent field,
$set will create the embedded documents as needed to fulfill the
dotted path to the field.
If you specify multiple field-value pairs, $set will update or create
each field.
So if you want to update an existing document by inserting elements into an array field, use the $push update operator (potentially with $each if you're inserting multiple elements):
let update_doc = doc! {
"$set": {
"edited_time": now,
"content": content
},
"$push": {
"changes": {
"time": now,
"change": {
"ChangedContent": "$content"
}
}
}
};
Edit: I missed that $content was supposed to be mapped from the existing field as well. That is not supported by an update document, however MongoDB has support for using an aggregation pipeline to update the document. See: Update MongoDB field using value of another field So you can use the original $set just in a different way:
let update_pipeline = vec![
doc! {
"$set": {
"changes": {
"$concatArrays": [
"$changes", [
{
"time": now,
"change": {
"ChangedContent": "$content"
}
}
]
]
},
"edited_time": now,
"content": content
}
}
];
messages.update_one(message_filter, update_pipeline, None).await?;
I know that by the title it is not very clear what is my problem, so let me explain it with an example.
Let's suppose I have a collection in a mongo database called tweets whose elements look like this:
{
"id": "tweet_id",
"text": "this is the tweet's text",
"user": {
"id": "user_id",
"name": "user_name",
}
}
Let's suppose that we have 100 documents that look like that, and 10 users with diferent ids and names.
How would look a query to know see the different user_id s that exist in the collection and their names?
The result I want would look like this:
{"user_id1": "user_name1"}
{"user_id2": "user_name2"}
...
{"user_id10": "user_name10"}
Thank you for your help
You can use this aggregation query:
First $group by user.id to get all differents user ids with the name.
And then use $replaceRoot with $arrayToObject to get the desired output format.
db.collection.aggregate([
{
"$group": {
"_id": "$user.id",
"name": {
"$first": "$user.name"
}
}
},
{
"$replaceRoot": {
"newRoot": {
"$arrayToObject": [
[
{
"k": "$_id",
"v": "$name"
}
]
]
}
}
}
])
Example here
Is there any way to give order or rankings to MongoDB aggregation results?
My result is:
{
"score":100
"name": "John"
},
{
"score":80
"name": "Jane"
},
{
"score":60
"name": "Lee"
}
My wanted result is:
{
"score":100
"name": "John",
"rank": 1
},
{
"score":80
"name": "Jane"
"rank": 2
},
{
"score":60
"name": "Lee"
"rank": 3
}
I know there is a operator called $includeArrayIndex but this only works with $unwind operator.
Is there any way to give rank without using $unwind?
Using $unwind requires grouping on my collection, and I'm afraid grouping pipeline would be too huge to process.
The other way is to use $map and add rank in document using its index, and don't use $unwind stage because it would be single field array you can directly access using its key name as mention in last line of code,
$group by null and make array of documents in root array,
$map to iterate loop of root array, get the index of current object from root array using $indexOfArray and increment that returned index number using $add because index start from 0, and that is how we are creating rank field, merge object with current element object and rank field using $mergeObjects
let result = await db.collection.aggregate([
{
$group: {
_id: null,
root: {
$push: "$$ROOT"
}
}
},
{
$project: {
_id: 0,
root: {
$map: {
input: "$root",
in: {
$mergeObjects: [
"$$this",
{
rank: { $add: [{ $indexOfArray: ["$root", "$$this"] }, 1] }
}
]
}
}
}
}
}
]);
// you can access result using root key
let finalResult = result[0]['root'];
Playground
I have:
{
"name": "A Name"
"ph": {"phone": "1111"}
"alt_ph": {"phone": "2222"}
}
I would like to query mongo in a way the result is like the below:
"A Name": ["1111", "2222"]
and if possible the list to be unique.
Not sure how to go about it
You can use $setUnion to make sure that your result contains unique values along with $replaceRoot combined with $arrayToObject to get your key evaluated dynamically based on other field's value:
db.collection.aggregate([
{
$replaceRoot: {
newRoot: {
$arrayToObject: [[ { k: "$name", v: { $setUnion: [ ["$ph.phone"], ["$alt_ph.phone"] ] } } ]]
}
}
}
])
Mongo Playground
Ok - I tried this & it's working, but not sure how to make it unique:
"$project": {
"_id": 0, "name": 1,
"phones": ["$ph", "$alt_ph"]
}
Gives me desired, but:
I will get null, if field is empty or field does not exist and i can get duplicates as well.
"session": {
"number": 123,
"words": {
"1": {
"id": 10,
"name": "Hello"
},
"2": {
"id": 13,
"name": "Hi"
},
"3": {
"id": 135,
"name": "Hey"
}
}
}
We have data in MongoDB database in the given structure which I am not able to modify.
I can get the object based on query session.number is 123, but now the challenging is we know the nested name is either Hi, Hey or Hello but the incremental key inside object words are unpredictable, is it possible to query base on the "name" field?
You can use $objectToArray and convert the words property to an array then query it however you want, you can use the following:
collection.aggregate([
{
$project: {
words: { $objectToArray: "$session.words" }
}
},
{
$match: {
'words.v': 'hi'
}
}
]);
You can read the docs for more info.