Querying

Query operations

As Casbah wraps the Java driver, so querying against MongoDB is essentially the same. The following methods for finding data:

• find Returns a cursor
• findOne Returns an Option - either Some(MongoDBObject) or None
• findById Returns an Option - either Some(MongoDBObject) or None
• findAndModify Finds the first document in the query, updates and returns it.
• findAndRemove Finds the first document in the query, removes and returns it.

The following methods insert and update data:

• save Saves an object to the collection
• insert Saves one or more documents to the collection
• update Updates any matching documents operation

For more information about create, read, update and delete (CRUD) operations in MongoDB see the core operations documentation.

The collection API documentation has a full list of methods and their signatures for interacting with collections.

Bulk Operations

Mongodb 2.6 introduces operations. The bulk operations builder can be used to construct a list of write operations to perform in bulk for a single collection. Bulk operations come in two main flavors.

1. Ordered bulk operations. These operations execute all the operation in order and error out on the first write error.
2. Unordered bulk operations. These operations execute all the operations in parallel and aggregates up all the errors. Unordered bulk operations do not guarantee order of execution.

An example of using the bulk api:

val collection = MongoClient()("test")("bulkOperation")

collection.drop()

val builder = collection.initializeOrderedBulkOperation
builder.insert(MongoDBObject("_id" -> 1))
builder.insert(MongoDBObject("_id" -> 2))
builder.insert(MongoDBObject("_id" -> 3))

builder.find(MongoDBObject("_id" -> 1)).updateOne($set("x" -> 2))
builder.find(MongoDBObject("_id" -> 2)).removeOne()
builder.find(MongoDBObject("_id" -> 3)).replaceOne(MongoDBObject("_id" -> 3, "x" -> 4))

val result = builder.execute()

For more information see the bulk operations documentation.

MongoDBObject

MongoDB queries work by providing a document to match against. The simplest query object is an empty one eg: MongoDBObject() which matches every record in the database.

MongoDBObject is a simple Map-like class, that wraps the Java driver DBObject and provides some nice Scala interfaces:

val query = MongoDBObject("foo" -> "bar") ++ ("baz" -> "qux")

DBObjects have a builder and as such you can also build MongoDBObjects that way:

val builder = MongoDBObject.newBuilder
builder += "foo" -> "bar"
builder += "baz" -> "qux"
val query = builder.result