I have a document for a user
bob = collection.find_one({'username':'bob'})
This returns to me a python dictionary,
print bob
>>{u'_id': ObjectId('542130bd43941e7878a8fa378'),
u'likes': {},
}
type(bob)
>> dict
So how can I do something like bob.update({'likes': {'sports':'football','movie':'terminator'}})
You are using update() incorrectly. update() updates a document within a collection. So you must call it on your collection, and pass it a dictionary that specifies the document you wish to update, and use the $set modifier to modify certain fields in the document you specified earlier.
Like this:
collection.update({'username': 'bob'}, {'$set': {'likes': {'sports': 'football', 'movie': 'terminator'}}})
Check out the documents here for more useful information regarding update(), as Salvador Dali already mentioned:
http://api.mongodb.org/python/current/api/pymongo/collection.html#pymongo.collection.Collection.update
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).
My records are something like this,
{
objectID: "123123",
product_id: "456456",
categories: ['pie', 'desert']
}
I want to just replace desert with sweet in categories.
Is this possible by using partial_update_objects method?
You can't update a value but ultimately you can Remove & Add with the built-in operations. It would allow an "update" of the value (it only works if the values in the array are unique). An alternative is to get the object and compute the new value for the array to later replace it.
What I intend to achieve is some sort of "live query" functionality.
So far I've tried using the "watch" method. According to the documentation:
You can open a stream of changes that match a filter by calling
collection.watch(delegate:) with a $match expression as the argument.
Whenever the watched collection changes and the ChangeEvent matches
the provided $match expression, the stream’s event handler fires with
the ChangeEvent object as its only argument
Passing the doc ids as an array works perfectly, but passing a query doesn't work:
this.stitch.db.collection<Queue>('queues')
.watch({
hospitalId: this.activehospitalid
}));
I've also tried this:
this.stitch.db.collection<Queue>('queues')
.watch({
$match: {
hospitalId: this.activehospitalid
}
},
));
Which throws an error on the console "StitchServiceError: mongodb watch: filter is invalid (unknown top level operator: $match)". The intention is watch all documents where the field "hospitalId" matches the provided value, or to effectively pass a query filter to the watch() method.
After a long search I found that it's possible to filter, but the query needs to be formatted differently
this.stitch.db.collection<Queue>('queues')
.watch({
$or: [
{
"fullDocument.hospitalId": this.activehospitalid
}
]
},
));
For anyone else who might need this, please note the important fullDocument part of the query. I havent found much documentation relating to this, but I hope it helps
I have an object structure like this:
{
name: "...",
pockets: [
{
cdate: "....",
items: [...]
}
...
]
}
In an update operation, I want to add some records into the items field of the last pocket item. Using dot notation is the only way that I know to access a sub document, but I can't get what I want. So, I'm looking for something like these:
pockets.-1.items
pockets.$last.items
Is it possible to modify the last element? If yes, how?
I don't know of a way to do this using a single-line query. But you could select the record, update and then save it.
var query = <insert query here>;
var mydocs = db.mycollection.find(query);
for (var i=0 ; i<mydocs.length ; i++) {
mydocs[i].pockets[pockets.length-1].items.push('new item');
db.mycollection.save(mydoc);
}
I don't believe it is possible to do it atomically. There is a request for this functionality to be added to MongoDB.
If you can assure thread-safety in your application code, you could probably use a sequence of $pop from pockets array (that removes the last element from pockets) to variable p and then $addToSet to p.items, now you can $push p back into pockets. But if your application doesn't have a way to assure only one process may be doing this at one time, then another process could modify the array in the middle of those steps and you may end up losing that update.
You might also look into "Update if current" semantics here to see another way you can work around possible race by multiple threads issue.
I know this has been asked before, but I have yet to find a solution that works efficiently. I am working with the MongoDB C# driver, though this is more of a general question about MongoDB operations.
I have a document structure that looks something like this:
field1: value1
field2: value2
...
users: [ {...user 1 subdocument...}, {...user 2 subdocument...}, ... ]
Some facts:
Each user subdocument includes further sub-arrays & subdocuments (so they're fairly complex).
The average users array only contains about 5 elements, but in the worst case can surpass 100.
Several thousand update operations on multiple users may be conducted per day in this system, each on one document at a time. Larger arrays will receive more frequent updates due to their data size.
I am trying to figure out how to do this efficiently. From what I've heard, you cannot directly set several array elements to new values all at once, so I had to try something else.
I tried using the $pullAll / $AddToSet + $each operations to remove the old array and replace it with a modified one. I am aware that $pullall can remove only the elements that I need as well, but I would like to preserve the order of elements.
The C# code:
try
{
WriteConcernResult wcr = collection.Update(query,
Update.Combine(Update.PullAll("users"),
Update.AddToSetEach("users", newUsers.ToArray())));
}
catch (WriteConcernException wce)
{
return wce.Message;
}
In this case newUsers is aList<BsonValue>converted to an array. However I am getting the following exception message:
Cannot update 'users' and 'users' at the same time
By the looks of it, I can't have two update statements in use on the same field in the same write operation.
I also tried Update.Set("users", newUsers.ToArray()), but apparently the Set statement doesn't work with arrays, just basic values:
Argument 2: cannot convert from 'MongoDB.Bson.BsonValue[]' to 'MongoDB.Bson.BsonValue'
So then I tried converting that array to a BsonDocument:
Update.Set("users", newUsers.ToArray().ToBsonDocument());
And got this:
An Array value cannot be written to the root level of a BSON document.
I could try replacing the whole document, but that seems like overkill and definitely not very efficient.
So the only thing I can think of now is to run two separate write operations: one to remove the unwanted old users and another to replace them with their newer versions:
WriteConcernResult wcr = collection.Update(query, Update.PullAll("users"));
WriteConcernResult wcr = collection.Update(query, Update.AddToSetEach("users", newUsers.ToArray()));
Is this my best option? Or is there another, better way of doing this?
Your code should work with a minor change:
Update.Set("users", new BsonArray(newUsers));
BsonArray is a BsonValue, where as an array of documents is not and we don't implicitly convert arrays like we do other primitive values.
this extension method solve my problem:
public static class MongoExtension
{
public static BsonArray ToBsonArray(this IEnumerable list)
{
var array = new BsonArray();
foreach (var item in list)
array.Add((BsonValue) item);
return array;
}
}