- Upgrade Guide
- Upgrading to 2.x
Migrating Your Application To 2.x
There are some key changes in the driver that you should be aware of before migrating your application from version 1.x to 2.x. Some APIs are cleaned up, and some 1.x features have been deprecated.
Design differences in 2.x
One major change is that the driver has been split into two pieces. There is a new mongodb-core
that contains the
low-level MongoDB APIs while mongodb
contains the high-level driver. mongodb-core
is targeted to creators of libraries like Mongoose and other ODMs who do not need the abstractions available in the mongodb
driver. The driver is
currently compatible with the 0.11.x Node.js branch, which includes support for Kerberos and MongoDB 3.0.
Changes
Below are listed some driver changes which could impact your application.
Node.js versions and Streams
The 2.0 driver drops support for 0.8.x style streams in favor of 0.10.x or higher style pull-based streams, which are
faster and more reliable. Backwards compatibility is available by using the readable-stream
npm package (might cause
some behavior changes for the cursor streams).
All dependencies have now been updated to use the nan
package. They will compile and work on 0.11.x or higher.
Grid Object
The grid object has been removed, due to its limited GridStore capabilities.
db Object
The db instance object has changed in several ways. The following methods have been removed:
db.dereference
due to db references being deprecated in the server.db.cursorInfo
removed as it never worked reliably.db.stats
removed as inconsistent.db.collectionNames
removed as it’s just a specialized version of the newlistCollections
helper.db.collectionInfo
removed as it’s not compatible with the new MongoDB 3.0 or higher alternative storage engines.
New method:
db.listCollections
to replace all other collection inquiry methods. It works with MongoDB 3.0 and higher and provide backwards compatibility for MongoDB 2.6 or lower.
Collection Object
The collection instance object has also changed in several key respects. Most importantly, we now return the mongodb-core
result objects directly, with all the associated information returned from the server, instead of the selective information returned in the 1.4.x version.
New methods:
collection.insertOne
insert a single document.collection.insertMany
insert an array of documents.collection.replaceOne
fully replace an existing document.collection.updateOne
update a single document.collection.updateMany
update multiple documents.collection.deleteOne
delete a single document.collection.deleteMany
delete multiple documents.collection.findOneAndUpdate
use findAndModify to update a document.collection.findOneAndDelete
use findAndModify to remove a specific document.collection.findOneAndReplace
use findAndModify to replace a specific document.
The current insert
, update
and remove
methods are marked for deprecation and will be removed in a future 3.0 driver. These three methods now return the full mongodb-core
results, and their third return value has been removed to ensure fewer compatibility problems with orchestration libraries like async
.
The insert methods are now capping at the maxWriteBatchSize
passed back from MongoDB on the results from the ismaster
command. For MongoDB 2.4 and lower this means a maximum of 1000 documents in each insert batch. Legacy insert mode has been deprecated in favor of proper emulation of current 2.6 or higher write commands.
Another important change is in how collection.find
works. The idea is to chain commands instead of passing them into the find
method. It still supports old behavior from 1.4 so no code should break, but the API documentation reflects the new, preferred way of using find
to execute queries.
GridStore
The GridStore object has changed in major ways, due to issues discovered by users related to parallel writing (using the previously available w+
append mode). As a result, in 2.0 w+
only allows for changes to the file metadata and does not allow for appending to a file, avoiding possible data corruption. The hope is to create a new GridStore spec in the future that allows for properly handling parallel writing to an existing file, but that will require changes for all drivers as well as the server.
MongoClient
MongoClient now has only the class method connect
. Construction of a new MongoClient using Server
, ReplSet
or Mongos
has been removed, due to the confusion it caused by duplicating the way one can build a topology connection using Db
in 1.4. MongoClient.connect
is the recommended way to connect to a MongoDB topology.