I have collection with following document structure:
{
_id: 1,
statuses: [
{
id:3, r:true, date:2016-02-01
},
{
id:2, r:false, date:2015-02-02
},
{
id:3, r:false, date:2015-02-03
}
]
}
How to find all elements from collection where r=false in LAST status where id=3.
If I could sort statuses by date descending, filter it by id=3 and take the first element... Maybe there is smarter way :)
Related
This has been extensively covered here, but none of the solutions seems to be working for me. I'm attempting to remove an object from an array using that object's id. Currently, my Schema is:
const scheduleSchema = new Schema({
//unrelated
_id: ObjectId
shifts: [
{
_id: Types.ObjectId,
name: String,
shift_start: Date,
shift_end: Date,
},
],
});
I've tried almost every variation of something like this:
.findOneAndUpdate(
{ _id: req.params.id },
{
$pull: {
shifts: { _id: new Types.ObjectId(req.params.id) },
},
}
);
Database:
Database Format
Within these variations, the usual response I've gotten has been either an empty array or null.
I was able slightly find a way around this and accomplish the deletion by utilizing the main _id of the Schema (instead of the nested one:
.findOneAndUpdate(
{ _id: <main _id> },
{ $pull: { shifts: { _id: new Types.ObjectId(<nested _id>) } } },
{ new: true }
);
But I was hoping to figure out a way to do this by just using the nested _id. Any suggestions?
The problem you are having currently is you are using the same _id.
Using mongo, update method allows three objects: query, update and options.
query object is the object into collection which will be updated.
update is the action to do into the object (add, change value...).
options different options to add.
Then, assuming you have this collection:
[
{
"_id": 1,
"shifts": [
{
"_id": 2
},
{
"_id": 3
}
]
}
]
If you try to look for a document which _id is 2, obviously response will be empty (example).
Then, if none document has been found, none document will be updated.
What happens if we look for a document using shifts._id:2?
This tells mongo "search a document where shifts field has an object with _id equals to 2". This query works ok (example) but be careful, this returns the WHOLE document, not only the array which match the _id.
This not return:
[
{
"_id": 1,
"shifts": [
{
"_id": 2
}
]
}
]
Using this query mongo returns the ENTIRE document where exists a field called shifts that contains an object with an _id with value 2. This also include the whole array.
So, with tat, you know why find object works. Now adding this to an update query you can create the query:
This one to remove all shifts._id which are equal to 2.
db.collection.update({
"shifts._id": 2
},
{
$pull: {
shifts: {
_id: 2
}
}
})
Example
Or this one to remove shifts._id if parent _id is equal to 1
db.collection.update({
"_id": 1
},
{
$pull: {
shifts: {
_id: 2
}
}
})
Example
I am fairly new to MongoDB and cant seem to find a solution to this problem.
I have a database of documents that has this structure:
{
id: 1
elements: [ {elementId: 1, nr1: 1, nr2: 3}, {elementId:2, nr1:5, nr2: 10} ]
}
I am looking for a query that can add a value nr3 which is for example nr2/nr1 to all the objects in the elements array, so that the resulting document would look like this:
{
id: 1
elements: [ {elementId: 1, nr1: 1, nr2: 3, nr3:3}, {elementId:2, nr1:5, nr2: 10, nr3: 2} ]
}
So I imagine a query along the lines of this:
db.collection.updateOne({id:1}, {$set:{"elements.$[].nr3": nr2/nr1}})
But I cant find how to get the value of nr2 and nr1 of the same object in the array.
I found some similar questions on stackoverflow stating this is not possible, but they were 5+ years old, so I thought maybe they have added support for something like this.
I realize I can achieve this with first querying the document and iterate over the elements-array doing updates along the way, but for the purpose of learning I would love to see if its possible to do this in one query.
You can use update with aggregation pipeline starting from MongoDB v4.2,
$map to iterate loop of elements
divide nr2 with nr1 using $divide
merge current object and new field nr3 using $mergeObjects
db.collection.updateOne(
{ id: 1 },
[{
$set: {
elements: {
$map: {
input: "$elements",
in: {
$mergeObjects: [
"$$this",
{ nr3: { $divide: ["$$this.nr2", "$$this.nr1"] } }
]
}
}
}
}
}]
)
Playground
db.collection.update(
{ id:1},
{ "$set": { "elements.$[elem].nr3":elements.$[elem].nr2/elements.$[elem].nr1} },
{ "multi": true }
);
I guess this should work
I have a problem in Mongo for which I am not getting any clue to resolve it efficiently.
Say I have a 'Course' collection something like this (index is created on the 'studentIds' field):
{
"courseId": 1,
"name": "Mathematics",
"studentIds": [1,3,5]
...
...
}
{
"courseId": 2,
"name": "Physics",
"studentIds": [2,3,5]
...
...
}
I am trying to write a query which would return records in the below format:
Say student 1 is querying the courses, he is enrolled for courseId 1, so the 'enrolled' is true, but student 1 not enrolled for courseId 2 and so the 'enrolled' is false:
{
"courseId": 1,
"name": "Mathematics",
"enrolled": true
}
{
"courseId": 2,
"name": "Physics",
"enrolled": false
}
Only solution I can think of is have two queries, first query to find all course IDs the student is enrolled in and while running through the cursor on the courses in the second query, add 'enrolled' field based on the existence of the courseId in the result of the first query, but looking for a way to achieve this in a single query.
Thanks.
You just need $in operator:
let studentId = 1;
db.collection.aggregate([
{
$project: {
courseId: 1,
name: 1,
enrolled: { $in: [ studentId, "$studentIds" ] }
}
}
])
Mongo Playground
I have a collection full of products each of which has a subdocument array of up to 100 variants (SKUs) of that product:
e.g.
{
'_id': 12345678,
'handle': 'my-product-handle',
'updated': false
'variants': [
{
'_id': 123412341234,
'sku': 'abc123',
'inventory': 1
},
{
'_id': 123412341235,
'sku': 'abc124',
'inventory': 2
},
...
]
}
My goal is to be able to update the inventory quantity of all instances of a SKU number. It is important to note that in the system I'm working with, SKUs are not unique. Therefore, if a SKU shows up multiple times in a single product or across multiple products, they all need to be updated to the new inventory quantity.
Furthermore, I need the "updated" field to be changed to "true" *only if the inventory quantity for that SKU has changed"
As an example, if I want to update all instances of SKU "abc123" to have 25 inventory, the example of above would return this:
{
'_id': 12345678,
'handle': 'my-product-handle',
'updated': true
'variants': [
{
'_id': 123412341234,
'sku': 'abc123',
'inventory': 25
},
{
'_id': 123412341235,
'sku': 'abc124',
'inventory': 2
},
...
]
}
Thoughts?
MongoDB 3.6 has introduced the filtered positional operator $[<identifier>] which can be used to update multiple elements of an array which match an array filter condition. You can read more about this operator here: https://docs.mongodb.com/manual/reference/operator/update/positional-filtered/
For example, to update all elements of the variants array where sku is "abc123" across every document in the collection:
db.collection.update({}, { $set: { "variants.$[el].inventory": 25 }}, { multi: true, arrayFilters: [{ "el.sku": "abc123"}] })
Unfortunately I'm not aware of any way in a single query to update a document's field based on whether another field in the document was updated. This is something you would have to implement with some client-side logic and a second query.
EDIT (thanks to Asya's comment):
You can do this in a single query by only matching documents which will be modified. So if nMatched and nModified are necessarily equal, you can just set updated to true. For example, I think this would solve the problem in a single query:
db.collection.update({ variants: { $elemMatch: { inventory: { $ne: 25 }, sku: "abc123" } } }, { $set: { "variants.$[el].inventory": 25, updated: true }}, { multi: true, arrayFilters: [{ "el.sku": "abc123"}] })
First you match documents where the variants array contains documents where the sku is "abc123" and the inventory does not equal the number you are setting it to. Then you go ahead and set the inventory on all matching subdocuments and set updated to true.
I have a collection in which unique documents from a different collection can appear over and over again (in example below item), depending on how much a user shares them. I want to create an aggregate query which finds the most shared documents. There is no $match necessary because I'm not matching a certain criteria, I'm just querying the most shared. Right now I have:
db.stories.aggregate(
{
$group: {
_id:'item.id',
'item': {
$first: '$item'
},
'total': {
$sum: 1
}
}
}
);
However this only returns 1 result. It occurs to me I might just need to do a simple find query, but I want the results aggregated, so that each result has the item and total is how many times it's appeared in the collection.
Example of a document in the stories collection:
{
_id: ObjectId('...'),
user: {
id: ObjectId('...'),
propertyA: ...,
propertyB: ...,
etc
},
item: {
id: ObjectId('...'),
propertyA: ...,
propertyB: ...,
etc
}
}
users and items each have their own collections as well.
Change the line
_id:'item.id'
to
_id:'$item.id'
Currently you group by the constant 'item.id' and therefore you only get one document as result.