I'm using MongoDB inside a twig framework. I'm trying to determine if the user has access to a certain module.
(a part of) my DB entry looks like:
_id: "579b50a4f5092761a20f4e71",
approvedModules: [
"examplemodule",
"examplemodule1",
"examplemodule2",
"examplemodule3"
],
My code looks like:
session.get('__AUTH_USER').find({ approvedModules : { '$in' : ["examplemodule"]}}, { '$exists' : true })
(the standard functions have to be in quotes).
I keeps returning false. I can only return the value if I use session.get('__AUTH_USER').approvedModules.0
I don't want to include the .0 because that might change.
What am I doing wrong?
Thanks in advance!
What am I doing wrong?
Many things. The worst one is using queries to database inside a template, but it is another problem.
You misunderstood purpose of the $in operator, which is used to match a field in the database to any element of array in the query.
To match any element of array in the collection to a single value you can do simple $eq:
session.get('__AUTH_USER').find({ approvedModules : "examplemodule"})
When you are using $in operator, you need to have 2 input arguments, the first one is the value for which you are checking the array, and the second one should be the array itself.
So, your bson element should look like this:
isModuleInArray : { '$in' : ["examplemodule","$approvedModules"] }
Related
TL;DR : Updating element in array always results in first element updated and results differ based on property name of key used in find params
Playground : https://mongoplayground.net/p/-4kGZnxa-WA
I want to update an object in a array and I am using 2 of the object properties to find the object then using $set operator with array.$.updateProperty to update the object
Here is the working playground link of what I want to do:
https://mongoplayground.net/p/dswt8vuzJMc
But I cant reproduce the same when I change a single property name (both in database as well as find parameter) , from the above example I changed property foo to trackID but then only the first element in array is always updated
Playground : https://mongoplayground.net/p/-4kGZnxa-WA
It seems weird as I assumed the property name shouldn't matter as long as it used the same in find params too and its not a keyword like _id
Your update is very close. You need to use "$elemMatch" to identify the specific array position where both conditions match.
N.B.: $ will only update the first matching array element. If you want to update all array elements, use $[], and if you want to update all matching array elements, using "arrayFilters" with $[<indentifier>] is convenient.
db.collection.update({
"_id": ObjectId("62f11e22d99c79532de6ff7f"),
"jobs": {
"$elemMatch": {
"trackID": 0,
"name": "kaisen_track-0_h264_1080p"
}
}
},
{
"$set": {
"jobs.$.status": "Done"
}
})
Try it on mongoplayground.net.
the documents looks like :
{
name: 'abc',
types: [
{name:'Large',stock:true},
{name:'XLarge',stock:false},
{name:'XXLarge',stock:true}
]
}
I'm trying to figure out the query to return all documents which are out of stock.
Something like : .find({types:{{$nin:{stock:true}}})
Can I somehow do that?
You can query using positional operator like this:
db.collection.find({'types.stock':{$ne:true}})
$nin operator is used for finding elements not in a particular array. $ne (not equal to) is a much better operation in your case.
I have a collection with following document:
{
"_id" : ObjectId("51f1fd2b8188d3117c6da352"),
"cust_id" : "abc1234",
"ord_date" : ISODate("2012-10-03T18:30:00Z"),
"status" : "A",
"price" : 27,
"items" : [{
"sku" : "mmm",
"qty" : 5,
"price" : 2.5
}, {
"sku" : "nnn",
"qty" : 5,
"price" : 2.5
}]
}
I want to use "$where" in the fields of "items", so something like this:
{$where:"this.items.sku==mmm"}
How can I do it? It works when the field is not of array type.
You don't need a $where operator to do this; just use a query object of:
{ "items.sku": mmm }
As for why your $where isn't working, the value of that operator is executed as JavaScript, so that's not going to check each element of the items array, it's just going to treat items as a normal object and compare its sku property (which is undefined) to mmm.
You are comparing this.items.sku to a variable mmm, which isn't initialized and thus has the value unefined. What you want to do, is iterate the array and compare each entry to the string 'mmm'. This example does this by using the array method some which returns true, when the passed function returns true for at least one of the entries:
{$where:"return this.items.some(function(entry){return entry.sku =='mmm'})"}
But really, don't do this. In a comment to the answer by JohnnyHK you said "my service is just a interface between user and mongodb, totally unaware what the field client want's to store". You aren't really explaining your use-case, but I am sure you can solve this better.
The $where operator invokes the Javascript engine even though this
trivial expression could be done with a normal query. This means unnecessary performance overhead.
Every single document in the collection is passed to the function, so when you have an index, it can not be used.
When the javascript function is generated from something provided by the client, you must be careful to sanetize and escape it properly, or your application gets vulnerable to code injection.
I've been reading through your comments in addition to the question. It sounds like your users can generically add some attributes, which you are storing in an array within a document. Your client needs to be able to query an arbitrary pair from the document in a generic manner. The pattern to achieve this is typically as follows:
{
.
.
attributes:[
{k:"some user defined key",
v:"the value"},
{k: ,v:}
.
.
]
}
Note that in your case, items is attributes. Now to get the document, your query will be something like:
eg)
db.collection.find({attributes:{$elemMatch:{k:"sku",v:"mmm"}}});
(index attributes.k, attributes.v)
This allows your service to provide a way to query the data, and letting the client specify what the k,v pairs are. The one caveat with this design is always be aware that documents have a 16MB limit (unless you have a use case that makes GridFS appropriate). There are functions like $slice which may help with controlling this.
I try to execute this query with perl on a MongoDB database :
$db->$collection->find({"_id" : { "$in" : ["4f520122ecf6171327000137", "4f4f49c09d1bd90728000034"]}});
But it return nothing and it must return two documents. What is wrong with this query ?
Thank you.
Edit : It doesn't work too :
$db->$collection->find( {_id => "4f520122ecf6171327000137"} );
First, make sure you're using the correct syntax. Your first example is not valid Perl code, since you're including a chunk of JSON as the query parameter.
Second, assuming these ID values are MongoDB ObjectID's, you'll need to make OID objects in order to differentiate them from ordinary strings. And make sure to use single quotes ('') around $in, otherwise Perl will try to interpolate $in as a variable (which presumably has nothing in it).
So I assume you want to do something like this:
$db->$collection->find( {
"_id" => {
'$in' => [ MongoDB::OID->new( value => "4f520122ecf6171327000137" ),
MongoDB::OID->new( value => "4f4f49c09d1bd90728000034" )
]
}
} );
Edit: Additionally, using autoloaded method names to retrieve collections has been deprecated for a while. You're better off using $db->get_collection( "collection name" )->find( ... )
I have a collection with entries that look like :
{
"userid": 1,
"contents": [
{ "tag": "whatever", "value": 100 },
{"tag": "whatever2", "value": 110 }
]
}
I'd like to be able to query on that collection and returning only one part of the array : the one matching the query. I'm trying to use the $ positional operator to do so but it hasn't worked so far.
Here is more precisely what I'd like to do :
collection.find({'contents.tag':"whatever"},{'contents.$.value':1})
As a result I expect sth with only the value corresponding to the entry in the array that matched query, which is 100 in this case.
Do you know what's wrong ? I was thinking that maybe the $ operator can only be used for update and not for querying. Anyone in the know ?
Thanks !
Yes, you are correct - the positional operator is used for updating an object.
The solution for now would be to return the array an pull the field out in your application.
There is an open enhancement request for this feature (in queries):
https://jira.mongodb.org/browse/SERVER-828
For more information on the positional operator, see:
http://www.mongodb.org/display/DOCS/Updating#Updating-The%24positionaloperator
What you are looking for is the $elemMatch operator.
It might be an overkill, but I guess you can use map-reduce for this.
first, pre-filter with a query, emit all array elements in map, filter the ones that do not match either in emit or in reduce. If you don't set out everything will happen in RAM.
If you have to run those kinds of queries often, it might be worthwhile to duplicate the data.
Nevertheless, I hope the SERVER-828 will be implemented soon!
Create a query with $in instead and add your equal value to the array, this can solve your issue
$users_array = array(xxxxxxxx,yyyyyy);
$user = Db::find('fb_users', array(
'facebook_id' => array(
'$in' => array($users_array)
)
));