How to Update a document by replacing it with a new document in a collection of mongoDB

Question

I am using ObjCMongoDB as a cocoa wrapper for accessing mongoDB. I am facing difficulty in a scenario where I have to find and replace a document with a new document. Can any one help me by pointing out the code/API of ObjCMongoDB to use.

For example:

{
"_id" : { "$oid" : "51de4ed737965b2d233f4862"} ,
"milestone" : "Application 7.1 release" ,
"pendingtasklist" : [ task1 , task2 , task3]
}

here I have to replace pendingtasklist with new list and result should be

{
"_id" : { "$oid" : "51de4ed737965b2d233f4862"} ,
"milestone" : "Application 7.1 release" ,
"someotherlist" : [ task12 , task33 , task32]
}

I have attached the code I am using to achieve this, but without success

NSError *connectionError = nil;
MongoConnection *dbConn = [MongoConnection connectionForServer:@"127.0.0.1:27017" error:&connectionError];


MongoDBCollection *collection = [dbConn collectionWithName:@"mydb.milestones"];

MongoKeyedPredicate *predicate = [MongoKeyedPredicate predicate];
[predicate keyPath:@"milestone" matches:@"Application 7.1 release"];

MongoUpdateRequest *updateReq = [MongoUpdateRequest updateRequestWithPredicate:predicate  firstMatchOnly:YES];
NSDictionary *milestoneDict = @{@"problemlist": @[@"12345",@"112244",@"55543",@"009009"],@"milestone":@"Application 7.1 release"};
[updateReq replaceDocumentWithDictionary:milestoneDict];

BOOL result = [collection updateWithRequest:updateReq error:&connectionError];

Before my collection will have documents like this:

{ "_id" : { "$oid" : "51de4ed737965b2d233f4862"} , "milestone" : "Application 7.1 Release" , "problemlist" : [ 12345 , 112244 , 55543]}
{ "_id" : { "$oid" : "51de4ed737965b2d233f4864"} , "milestone" : "Application 7.1 UAT" ,  "problemlist" : [ 33545 , 7654 , 8767]}

The above code works perfectly, there was a extra space in the string while creating the predicate. — Kiran Balegar, Jul 25 '13 at 13:42

score 1 · Accepted Answer · answered Jul 24 '13 at 16:40

1

If the value were staying the same, you would just rename the key:

-[MongoUpdateRequest keyPath:renameToKey:]

But since the values are changing, you should just unset the old key and set the new one.

-[MongoUpdateRequest unsetValueForKeyPath:]
-[MongoUpdateRequest keyPath:setValue:]

As I mentioned above you can do this with a single update request.

answered Jul 24 '13 at 16:40

paulmelnikow

16,895
8
63
114

1

The string for milestone doesn't match your sample data, which has an extra space before Release. To add values to an array, use -arrayForKeyPath:appendValuesFromArray: instead. What exactly is happening? What are the values of result, and of connectionError? – paulmelnikow Jul 25 '13 at 11:41
Basically in a my collection, I have lot of documents which has lot of key:values. In update I dont want to check each field in a document and write query to update the document. Instead I want to replace the document with a updated document which might have some new key:value added or deleted. Hope I am clear this time :) And the BOOL result will be YES but the DB is not getting updated. – Kiran Balegar Jul 25 '13 at 12:16
Found it! as u said there was a typo with my string and db document. Thanks a lot :) – Kiran Balegar Jul 25 '13 at 13:39
Is ObjCMongoDB thread safe? I have like 200 asynchronous operations executing and all of them has DB Insert/Update as their last task. Thanks! – Kiran Balegar Jul 29 '13 at 13:00

score 0 · Answer 2 · answered Jul 24 '13 at 15:52

0

In order to rename a field, you need to remove the old one, and add the new one. In this case, you would have to run two separate queries for this.

answered Jul 24 '13 at 15:52

Derick

35,169
5
76
99

First sentence yes; second sentence no. In Mongo, you can make multiple changes to a document with a single update request. – paulmelnikow Jul 24 '13 at 16:36

How to Update a document by replacing it with a new document in a collection of mongoDB

2 Answers2