is there a preferred way to check for existing documents via mongoid?
if i do Model.find('id')', and the id is nil or the document doesn't exist, it throws an exception... i want it to return an empty array.
if i do Model.where(:id => 'id'), and the id is nil, it returns all the documents... i also want it to return an empty array.
and then with Model.criteria(:id => 'id').to_a, for whatever reason never returns a result, even with a valid object id. not sure what is going on there...
but basically with activerecord i would just use the exists? finder method, so i am looking for the mongoid alternative.
In Mongoid 2.0, Following seems to do what you want:
User.all.for_ids('4d9ad01de1607c4bc000001a').entries
Related
I am completely mystified (and supremely frustrated). How do I create this call using the mongoc library?
I have the following doc structure in the collection
{_id: myOID,
subsriptions: {
newProducts: true,
newBlogPosts: true,
pressReleases: true,
}
}
I want to remove one of the subscriptions, for example, the user no longer wants to receive press releases from me.
This works in the mongo shell. Now I need to do it in C code
updateOne({_id: myOID}, [{'$unset': 'subscriptions.pressReleases'}], {})
Note how the update parameter in the Mongo shell is an anonymous array. I need to do that for the bson passed in as the update parameter in the mongoc_collection_update_one() API call.
The C code for updateOne is
mongo_status = mongoc_collection_update_one (mongo_collection,
mongo_query,
mongo_update,
NULL, /* No Opts to pass in */
NULL, /* no reply wanted */
&mongo_error);
Also note that in the aggregate() API, this is done with
{"pipeline" : [{'$unset': 'elists.lunch' }] }
Neither the updateOne() shell function nor the mongoc_collection_update_one() API call accept that, they want just the array.
How do I create the bson to use as the second parameter for mongoc_collection_update_one() API call?
Joe's answer works and I am able to accomplish what I need to do.
The $unset update operator takes an object, just like $set.
updateOne({_id: myOID},{'$unset':{'subscriptions.pressReleases': true}})
OR perhaps even better
updateOne({_id: myOID},{'$unset':{'subscriptions.pressReleases': {'$exists': true}}})
which will remove the subscription flag no matter what the value is for that field.
Doing it this way does not require an anonymous array (which I still don't know how to create).
This Meteor code needs to check if a certain document exist in the collection by checking if a cursor is returned, and if no cursor returned then the document does not exist. but it always returns true even if there is no value "alosh" for the text field in any of the documents in the collection
.
Why and how can it be fixed? Thanks
if (myCollection.find({text: 'alosh'}, {limit: 1})) {console.log('found');}
edit
The reason I did not use colllection.findOne is my understanding that it is much slower according to this post
Idea for solution:
You want to understand if there is a document with a certain value for a certain property. You could use:
if(myCollection.findOne({text: 'alosh'})){
console.log("found");}
Add a count. A cursor is always going to be a truthy value as the cursor itself is returned. You need to check the records contained in the cursor so...
if (myCollection.find({text: 'alosh'}, {limit: 1}).count()) {
console.log('found');
}
Because no docs returned is 0 and 0 is falsey this should only return when documents are found
Mongo cursors seem to behave the same as arrays in that an empty cursor (and an empty array) evaluate to true.
So !![] //true and !!collection.find({text : "alosh"}) //true.
BUT collection.findOne({text : "alosh"}) will fail your if - so use that instead
http://docs.meteor.com/#/full/findone
I want to be able to search for my objects by searching for the last 4 characters of the id. How can I do that?
Book.where(_id: params[:q])
Where the param would be something like a3f4, and in this case the actual id for the object that I want to be found would be:
bc313c1f5053b66121a8a3f4
Notice the last for characters are what we searched for. How can I search for just "part" of my objects id? instead of having my user search manually by typing in the entire id?
I found in MongoDB's help docs, that I can provide a regex:
db.x.find({someId : {$regex : "123\\[456\\]"}}) // use "\\" to escape
Is there a way for me to search using the regular mongo ruby driver and not using Mongoid?
Usually, in Mongoid you can search with a regexp like you normally would with a string in your call to where() ie:
Book.where(:title => /^Alice/) # returns all books with titles starting with 'Alice'
However this doesn't work in your case, because the _id field is not stored as a string, but as an ObjectID. However, you could add (and index) a field on your models which could provide this functionality for you, which you can populate in an after_create callback.
<shameless_plug>
Alternatively, if you're just looking for a shorter solution to the default Mongoid IDs, I could suggest something like mongoid_token which makes it pretty easy to add shorter tokens/ids to your Mongoid documents.
</shameless_plug>
Im trying to 'compare' all documents between 2 collections, which will return true only and if only all documents inside 2 collections are exactly equal.
I've been searching for the methods on the collection, but couldnt find one that can do this.
I experimented something like these in the mongo shell, but not working as i expected :
db.test1 == db.test2
or
db.test1.to_json() == db.test2.to_json()
Please share your thoughts ! Thank you.
You can try using mongodb eval combined with your custom equals function, something like this.
Your methods don't work because in the first case you are comparing object references, which are not the same. In the second case, there is no guarantee that to_json will generate the same string even for the objects that are the same.
Instead, try something like this:
var compareCollections = function(){
db.test1.find().forEach(function(obj1){
db.test2.find({/*if you know some properties, you can put them here...if don't, leave this empty*/}).forEach(function(obj2){
var equals = function(o1, o2){
// here goes some compare code...modified from the SO link you have in the answer.
};
if(equals(ob1, obj2)){
// Do what you want to do
}
});
});
};
db.eval(compareCollections);
With db.eval you ensure that code will be executed on the database server side, without fetching collections to the client.
This is the sample code :
$r = $coll->findOne();
$coll->remove(array("_id"=>$r["_id"])); // use the same object id as retreived from DB
$ret=$coll->findOne(array("_id"=>($r["_id"])));
var_dump($ret); // dumps the records that was supposed to be deleted
The records in the collection have MongoDB objectId, and not strings.
Same logic on console works fine and deleted the record correctly.
This is working for me. Here's the code:
$coll->drop();
print("Now have ".$coll->count()." items\n");
$coll->insert(array("x" => 'blah'));
$coll->insert(array("x" => "blahblah"));
print("Inserted ".$coll->count()." items\n");
$x = $coll->findOne();
print("Object X\n");
print_r($x);
$query_x = array('_id' => $x['_id']);
$coll->remove($query_x);
print("Removed 1 item, now have ".$coll->count()." items\n");
$y = $coll->findOne($query_x);
print("Object Y\n");
print_r($y);
Here's the output:
Now have 0 items
Inserted 2 items
Object X
Array
(
[_id] => MongoId Object
(
[$id] => 4d8d124b6803fa623b000000
)
[x] => blah
)
Removed 1 item, now have 1 items
Object Y
Are you sure there's not a typo somewhere?
Unlike the php == operator, mongo's equality operator always uses "Object equality" which is like php's identical comparison operator (===) or java's .equals(). While your code looks as though it should work (and it does work fine for me with a test dataset), something about your dataset may be causing php to cast the returned MongoId to a string. Read more about MongoId here.
Make sure that your query is supplying a MongoId for comparison by doing a var_dump of the query itself. Also, make sure that you are running the latest version of the PHP Mongo driver.
Since PHP is loosely typed it is most important to ensure that you cast all input values and search values to the expected and consistent data type otherwise it will surely not locate your expected document.
While using MongoDB within PHP I make it a point to cast everything intentionally in order to avoid any possible confusion or error.
Also, the mongodb-user group at groups.google.com is very good and responsive so if you are not already utilizing that resource I would definitely consider joining it.