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.
Related
I've two mongo collections - File and Folder.
Both have some common fields like name, createdAt etc. I've a resources API that returns a response having items from both collections, with a type property added. type can be file or folder
I want to support pagination and sorting in this list, for example sort by createdAt. Is it possible with aggregation, and how?
Moving them to a container collection is not a preferred option, as then I have to maintain the container collection on each create/update/delete on either of the collection.
I'm using mongoose too, if it has got any utility function for this, or a plugin.
In this case, you can use $unionWith. Something like:
Folder.aggregate([
{ $project: { name: 1, createdAt: 1 } },
{
$unionWith: {
coll: "files", pipeline: [ { $project: { name: 1, createdAt: 1 } } ]
}
},
... // your sorting go here
])
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 find in array of object and match _id and is_active both key
ex
{
_id:'12333333333333'
name:'test',
array:[{
id:'1233449',
is_active:true
},{
id:'7987979',
is_active:false
},{
id:'9558555',
is_active:true
},{
id:'2564654',
is_active:false
}]
}
find data using mongo query
db.getCollection('demo').find({'array.id':'7987979','array.is_active':false});
not working
The reason it isnt working for you is because you are running a find operation on the array directly.
When querying for things within an array you can use $elemMatch to obtain an entire document that contains the matching array element.
If you need a custom output you can use Aggregation, with the $unwind operation in the pipeline on the array field.
Try this out on your collection and understand what it is doing
db.collectionName.aggregate([{
$unwind:"$array"
},{
$match:{
$and:[
{"array.id":'your_id'},
{"array.is_active":boolean}
]
}
}
])
Im using NodeJs, MongoDB Native 2.0+
The following query fetch one client document containing arrays of embedded staff and services.
db.collection('clients').findOne({_id: sessId}, {"services._id": 1, "staff": {$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}}
])
In MongoDB, is there any easy way to check Order of element in Array? For example I have a document like this:
{
_id: 1,
tags: ["mongodb", "rethinkdb", "couchbase", "others"]
}
I would like to check in tags field if mongodb come before rethinkdb or not(lets see in array element, mongodb=0, rethinkdb=1 index, so mongodb come first and our case match.)?
but if there is another document (like below) where rethinkdb comes before mongodb,It case does not match.
{
_id: 2,
tags: ["rethinkdb", "mongodb", "couchbase"]
}
Here mongodb(1) comes after rethinkdb(0) so our case does not match.
Your question is not really as clear as you think it is, and thus why there are several ways to answer it:
If you are looking just to find out if a document has "mongodb" as the first element of the array then you just issue a query like this:
db.collection.find({ "tags.0": "mongodb" })
And that will return only the documents that match the given value at the specified index position using "dot notation".
If you actually expect to match if an array is in an "expected order" then you can get some help from the aggregation pipeline and set operators that are available and other features in MongoDB 2.6:
db.collection.aggregate([
{ "$project": {
"$_id": "$$ROOT",
"matched": { "$setEquals": [
"$tags",
["mongodb", "rethinkdb", "couchbase", "others"]
]}
}},
{ "$match": { "matched": true }}
])
Or if your want is to make sure that the "mongodb" value comes before the "rethinkdb" value, then you will need to evaluate in JavaScript with mapReduce, or something equally not nice like the $where operator:
db.collection.find({
"$where": function() {
return this.tags.indexOf("mongodb") < this.tags.indexOf("rethinkdb");
}
})