In mongo I have a collections with records. These record are very complex. Now I would like to duplicate one of them.
I can easily select the one
mongo> var row = db.barfoo.find({"name":"bar"});
Now I actually don't know what to do. I don't know what is in row because I cannot find a way to print its content. How can I change specific properties and finally insert this modified row again
mongo> db.barfoo.insert(row);
thnx
You must change value _id - generate new:
var row = db.barfoo.findOne({"name":"bar"});
row._id = ObjectId();
db.barfoo.insert(row);
Good Luck!
I am going to assume that you're working directly inside the mongo shell.
Once you have your document (not a row :P ), you'd modify the properties in the same way you would a normal JavaScript object:
var doc = db.barfoo.findOne( { "name": "bar" } );
doc.name = "Mr Bar";
Note that the find() command returns a cursor, so if you're looking to extract a single document, you should use the findOne() function. This function returns a single document.
If you are interested in duplicating numerous documents, you can use the find() function and iterate over the cursor to retrieve each document:
db.barfoo.find( { "name": "bar" } ).forEach( function( doc ){
doc.name = "Mr Bar";
}
After you change the relevant properties, you can use the insert/save methods to persist the data back to mongo. Don't forget to change/delete the _id attribute so that you'll actually create a new document.
As a side note, in order to view the contents of an object in the mongo shell, you can use the print() function. If you want a more visually appealing output, you could use printjson().
Related
Why dosen't db.find work? The console.log gets undefined...
var course = (db.courses.find({ _id: mongo.helper.toObjectID(param.course)}));
console.log(course.body)
The way you are trying use Selects documents in a collection and returns a cursor to the selected documents., so you can't use the way you are trying to use it.
You need to use a callback() to get the records matching the query.
The below code will give result in an array format :-
db.courses.findOne({ _id: mongo.helper.toObjectID(param.course)}).toArray(function(err, result)
{
console.log(result[0]); // will give you the matched record.
})
Alright, so I have a collection called Polls. Inside the Polls "table" there is an attribute called choiceObjects which is an array of objects. Each object inside this array has its own attributes. What I need to do is update one of the attributes there. Ill give you a screen shot so you can better visualise what Im talking about
As you can see the choice objects have attributes like body, country etc. There is another attribute called pollid which is set to optional and therefore you cant see it right now. I need to update this pollid attribute now that I have acess to the pollid
Polls.update(
{ _id: pollId },
{ "$set": { "choiceObjects": { pollid: pollId } } }
); //this is kind of what Im trying to do but this isnt right
Since then... I have further tried the following :
var selectedpoll = Polls.findOne(pollId);
console.log(selectedpoll);
//Polls.update( selectedpoll, {"$set"{'choiceObjects.$.pollId':pollId}},false, true );
but when i try that i get the error : the positional operator did not find the match needed from the query. unexpanded update: choiceObjects.$.pollId
If I understand your objective correctly, you want to update (or add) pollid to all objects in the choiceObjects array. Unfortunately $, $push, $addToSet only work with single elements AFAIK.
This might not be what you are looking for but one possible and very obvious way to approach this problem would be to update the entire array in the collection i.e.
var choiceObjects = Polls.findOne({_id: pollId}).choiceObjects;
for (var i = 0; i < choiceObjects.length; i++) {
choiceObjects[i].pollid = pollid;
}
Polls.update({_id: pollid}, {choiceObjects: choiceObjects});
I have a collection which have a document like this:
collection 1
{
_id: ObjectID(),
name: foo
}
I would get ObjectID of the above collection and copy into a document of another collection in order to reference correctly. Should I do simply:
db.collection1.find({name:"foo"},{_id:1})
EDIT
A call to find will return a cursor. Cursors works like an iterator in other languages. You can either attempt to find the first element in the cursor using the next() function and then get it's _id property or simplify your statement using findOne:
var x = db.collection1.findOne({name:"foo"}, {_id:1});
var id = x._id;
This is making an assumption that you are getting a document back from that query. You'll probably want to add a null check on x before grabbing the _id property.
I have a local collection that logs when a user has viewed an entry. It stores the ID of the entry and the time it was viewed:
viewedDate = new Date();
notifications.insert({
'viewed': this.data._id,
'viewedDate': viewedDate
});
I want to exclude any of the 'viewed' ids in this collection from another find() (I basically want to count how many entries haven't been viewed)
How can I use the results of a notifications.find() to exclude results from another find()? If I assign the notifications.find() to a variable, it returns all kinds of stuff as an object.
edit
OK, so if I use fetch() I can restrict what comes back - can I do something with this in a find()?
myNotes = notifications.find({}, {fields: {'viewedDate' :0, _id:0}}).fetch();
This returns
[
Object
viewed: "HqYcCma3qKseHALyv"
__proto__: Object
]
Thanks to some invaluable help from garilla_ in the Meteor IRC, I got it working, solution as follows:
myViewedOffers = notifications.find({},{fields: {'viewed':1}}).fetch();
myViewedArray = myViewedOffers.map(function(viewed){return viewed.viewed});
offerCount = Offers.find({_id: {$nin: myViewedArray}}).count();
I'm new to Mongo, and I'm trying to retrieve the first document from a find() query:
> db.scores.save({a: 99});
> var collection = db.scores.find();
[
{ "a" : 99, "_id" : { "$oid" : "51a91ff3cc93742c1607ce28" } }
]
> var document = collection[0];
JS Error: result is undefined
This is a little weird, since a collection looks a lot like an array. I'm aware of retrieving a single document using findOne(), but is it possible to pull one out of a collection?
The find method returns a cursor. This works like an iterator in the result set. If you have too many results and try to display them all in the screen, the shell will display only the first 20 and the cursor will now point to the 20th result of the result set. If you type it the next 20 results will be displayed and so on.
In your example I think that you have hidden from us one line in the shell.
This command
> var collection = db.scores.find();
will just assign the result to the collection variable and will not print anything in the screen. So, that makes me believe that you have also run:
> collection
Now, what is really happening. If you indeed have used the above command to display the content of the collection, then the cursor will have reached the end of the result set (since you have only one document in your collection) and it will automatically close. That's why you get back the error.
There is nothing wrong with your syntax. You can use it any time you want. Just make sure that your cursor is still open and has results. You can use the collection.hasNext() method for that.
Is that the Mongo shell? What version? When I try the commands you type, I don't get any extra output:
MongoDB shell version: 2.4.3
connecting to: test
> db.scores.save({a: 99});
> var collection = db.scores.find();
> var document = collection[0];
In the Mongo shell, find() returns a cursor, not an array. In the docs you can see the methods you can call on a cursor.
findOne() returns a single document and should work for what you're trying to accomplish.
So you can have several options.
Using Java as the language, but one option is to get a db cursor and iterate over the elements that are returned. Or just simply grab the first one and run.
DBCursor cursor = db.getCollection(COLLECTION_NAME).find();
List<DOCUMENT_TYPE> retVal = new ArrayList<DOCUMENT_TYPE>(cursor.count());
while (cursor.hasNext()) {
retVal.add(cursor.next());
}
return retVal;
If you're looking for a particular object within the document, you can write a query and search all the documents for it. You can use the findOne method or simply find and get a list of objects matching your query. See below:
DBObject query = new BasicDBObject();
query.put(SOME_ID, ID);
DBObject result = db.getCollection(COLLECTION_NAME).findOne(query) // for a single object
DBCursor cursor = db.getCollection(COLLECTION_NAME).find(query) // for a cursor of multiple objects