This question already has an answer here:
MongoDB daily data inside array
(1 answer)
Closed last year.
I have this kind of structure in mongoDB
my schema
{
user: String,
skills: Array
}
for every user How to search all users by a particular skill
You can use the $in operator
db.collection.find({ skills: { $in: ['programming', 'cooking'] }})
or Mongoose models.
Model.find({ skills: { $in: ['programming', 'cooking'] }})
https://docs.mongodb.com/manual/reference/operator/query/in/
Related
I have a short but important question. I am new to MongoDB and querying.
My database looks like the following: I only have one document stored in my database (sorry for blurring).
The document consists of different fields:
two are blurred and not important
datum -> date
instance -> Array with an Embedded Document Object; Our instance has an id, two not important fields and a code.
Now I want to query how many times an object in my instance array has the group "a" and a text "sample"?
Is this even possible?
I only found methods to count how many documents have something...
I am using Mongo Compass, but i can also use Pymongo, Mongoengine or every other different tool for querying the mongodb.
Thank you in advance and if you have more questions please leave a comment!
You can try this
db.collection.aggregate([
{
$unwind: "$instance"
},
{
$unwind: "$instance.label"
},
{
$match: {
"instance.label.group": "a",
"instance.label.text": "sample",
}
},
{
$group: {
_id: {
group: "$instance.label.group",
text: "$instance.label.text"
},
count: {
$sum: 1
}
}
}
])
I want to update nested _ids over an entire collection IF they are of a type string.
If I have object that look like this...
user : {
_id: ObjectId('234wer234wer234wer'),
occupation: 'Reader',
books_read: [
{
title: "Best book ever",
_id: "123qwe234wer345ert456rty"
},
{
title: "Worst book ever",
_id: "223qwe234wer345ert456rty"
},
{
title: "A Tail of Two Cities",
_id: ObjectId("323qwe234wer345ert456rty")
}
]
}
and I want to change the type of the _Ids from string to ObjectId
how would I do that.??
I have done "this" in the past...But this is working on NON-nested item - I need to change a nested value
db.getCollection('users')
.find({
$or: [
{occupation:{$exists:false}},
{occupation:{$eq:null}}
]
})
.forEach(function (record) {
record.occupation = 'Reader';
db.users.save(record);
});
Any help - I am trying to avoid writing a series of loop on the app server to make db calls - so I am hoping for something directly in 'mongo'
There isn't a way of doing (non $rename) updates operations on a document while referencing existing fields -- MongoDB: Updating documents using data from the same document
So, you'll need to write a script (similar to the one you posted with find & each) to recreate those documents with the correct _id type. To find the subdocuments to update you can use the $type operator. A query like db.coll.find({nestedField._id: {$type: 'string' }}) should find all the full documents that have bad subdocuments, or you could do an aggregation query with $match & $unwind to only get the subdocuments
db.coll.aggregate([
{ $match: {'nestedField._id': {$type: 'string' }}}, // limiting to documents that have any bad subdocuments
{ $unwind: '$nestedField'}, // creating a separate document in the pipeline for each entry in the array
{ $match: {'nestedField._id': {$type: 'string' }}}, // limiting to only the subdocuments that have bad fields
{ $project: { nestedId: 'nestedField._id' }} // output will be: {_id: documentedId, nestedId }
])
I am trying to avoid writing a series of loop on the app server to make db calls - so I am hoping for something directly in 'mongo'
You can run js code directly on the mongo to avoid making api calls, but I don't think there's any way to avoid looping over the documents.
This question already has answers here:
Retrieve only the queried element in an object array in MongoDB collection
(18 answers)
Closed 5 years ago.
I have the following schema:
{
_id: objectID('593f8c591aa95154cfebe612'),
name: 'test'
businesses: [
{
_id: objectID('5967bd5f1aa9515fd9cdc87f'),
likes: [objectID('595796811aa9514c862033a1'), objectID('593f8c591ba95154cfebe790')]
}
{
_id: objectID('59579ff91aa9514f600cbba6'),
likes: [objectID('693f8c554aa95154cfebe146')]
}
]
}
How can I check if objectID('593f8c591ba95154cfebe790') exists in the array business.likes where businesses._id = objectID('59579ff91aa9514f600cbba6') ?
In the above example it should return false.
You can use $elemMatch to find by multiple field in same sub document
db.collectionName.find({
businesses: {
$elemMatch: {
_id: ObjectId("5967bd5f1aa9515fd9cdc87f"),
likes: ObjectId("593f8c591ba95154cfebe790")
}
}
});
I'm having a Meteor chat application and try to delete all chats when a user removes the friendship. At the moment, I'm using this:
Friends.before.remove(function (userId, doc) {
// Delete Chats
Chats.find({users: {$elemMatch: {id: doc.user1, id: doc.user2}}}).forEach(function (docx) {
Chats.remove(docx._id);
})
});
Problem here: This code deletes ALL chats of a user, and not only the one where the match is correct. My chat document has a structure like this:
Chat
created_at: Date
users: [ {id: 'abc'}, {id: 'def'}]
last_message: Date
How can I remove all chats, that have both users in their arrays?
Use $all operator instead of $elemMatch.
$all
The $all operator selects the documents where the value of a field is an array that contains all the specified elements. To specify an $all expression, use the following prototype:
{ <field>: { $all: [ <value1> , <value2> ... ] } }
See MongoDB Docs.
Im using NodeJs, MongoDB Native 2.0+
The following query fetch one client document containing arrays of embedded staff and services.
db.collection('clients').findOne({_id: sessId}, {"services._id": 1, "staff": {$elemMatch: {_id: reqId}}}, callback)
Return a result like this:
{
_id: "5422c33675d96d581e09e4ca",
staff:[
{
name: "Anders"
_id: "5458d0aa69d6f72418969428"
// More fields not relevant to the question...
}
],
services: [
{
_id: "54578da02b1c54e40fc3d7c6"
},
{
_id: "54578da42b1c54e40fc3d7c7"
},
{
_id: "54578da92b1c54e40fc3d7c9"
}
]
}
Note that each embedded object in services actually contains several fields, but _id is the only field returned by means of the projection of the query.
From this returned data I start by "pluck" all id's from services and save them in an array later used for validation. This is by no means a difficult operation... but I'm curious... Is there an easy way to do some kind of aggregation instead of find, to get an array of already plucked objectId's directly from the DB. Something like this:
{
_id: "5422c33675d96d581e09e4ca",
staff:[
{
name: "Anders"
_id: "5458d0aa69d6f72418969428"
// More fields not relevant to the question...
}
],
services: [
"54578da02b1c54e40fc3d7c6",
"54578da42b1c54e40fc3d7c7",
"54578da92b1c54e40fc3d7c9"
]
}
One way of doing it is to first,
$unwind the document based on the staff field, this is done to
select the intended staff. This step is required due to the
unavailability of the $elemMatch operator in the aggregation
framework.
There is an open ticket here: Jira
Once the document with the correct staff is selected, $unwind, based on $services.
The $group, together $pushing all the services _id together in an array.
This is then followed by a $project operator, to show the intended fields.
db.clients.aggregate([
{$match:{"_id":sessId}},
{$unwind:"$staff"},
{$match:{"staff._id":reqId}},
{$unwind:"$services"},
{$group:{"_id":"$_id","services_id":{$push:"$services._id"},"staff":{$first:"$staff"}}},
{$project:{"services_id":1,"staff":1}}
])