Package com.mongodb.operation

Class GroupOperation<T>

java.lang.Object

com.mongodb.operation.GroupOperation<T>

Type Parameters:

T - the operations result type.

All Implemented Interfaces:

AsyncReadOperation<AsyncBatchCursor<T>>, ReadOperation<BatchCursor<T>>

public class GroupOperation<T>
extends Object
implements AsyncReadOperation<AsyncBatchCursor<T>>, ReadOperation<BatchCursor<T>>

Groups documents in a collection by the specified key and performs simple aggregation functions, such as computing counts and sums. The command is analogous to a SELECT ... GROUP BY statement in SQL.

Since:

3.0

MongoDB documentation

Group Command

Constructor Summary

Constructors

Constructor	Description
GroupOperation(MongoNamespace namespace, BsonJavaScript reduceFunction, BsonDocument initial, Decoder<T> decoder)	Create an operation that will perform a Group on a given collection.

Method Summary

Modifier and Type	Method	Description
GroupOperation<T>	collation(Collation collation)	Sets the collation options
BatchCursor<T>	execute(ReadBinding binding)	Will return a cursor of Documents containing the results of the group operation.
void	executeAsync(AsyncReadBinding binding, SingleResultCallback<AsyncBatchCursor<T>> callback)	General execute which can return anything of type T
GroupOperation<T>	filter(BsonDocument filter)	Sets the optional query filter to determine which documents in the collection to process.
GroupOperation<T>	finalizeFunction(BsonJavaScript finalizeFunction)	Sets the function that runs each item in the result set before returning the final value.
Collation	getCollation()	Returns the collation options
Decoder<T>	getDecoder()	Gets the decoder used to decode the result documents.
BsonDocument	getFilter()	Gets the query filter to determine which documents in the collection to process.
BsonJavaScript	getFinalizeFunction()	Gets the function that runs each item in the result before returning the final value.
BsonDocument	getInitial()	Gets the initial the aggregation result document.
BsonDocument	getKey()	Gets the document containing the field or fields to group.
BsonJavaScript	getKeyFunction()	Gets the function that creates a "key object" for use as the grouping key.
MongoNamespace	getNamespace()	Gets the namespace.
BsonJavaScript	getReduceFunction()	Gets the aggregation function that operates on the documents during the grouping operation.
GroupOperation<T>	key(BsonDocument key)	Sets the document containing the field or fields to group.
GroupOperation<T>	keyFunction(BsonJavaScript keyFunction)	Sets the function that creates a "key object" for use as the grouping key.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

GroupOperation

public GroupOperation(MongoNamespace namespace,
                      BsonJavaScript reduceFunction,
                      BsonDocument initial,
                      Decoder<T> decoder)

Create an operation that will perform a Group on a given collection.

Parameters:

namespace - the database and collection namespace for the operation.

reduceFunction - The aggregation function that operates on the documents during the grouping operation.

initial - The initial the aggregation result document.

decoder - the decoder for the result documents.

MongoDB documentation

Group Command

Method Detail

getNamespace

public MongoNamespace getNamespace()

Gets the namespace.

Returns:

the namespace

Since:

3.4

getDecoder

public Decoder<T> getDecoder()

Gets the decoder used to decode the result documents.

Returns:

the decoder

Since:

3.4

getKey

public BsonDocument getKey()

Gets the document containing the field or fields to group.

Returns:

the document containing the field or fields to group.

key

public GroupOperation<T> key(BsonDocument key)

Sets the document containing the field or fields to group.

Parameters:

key - the document containing the field or fields to group.

Returns:

this

getKeyFunction

public BsonJavaScript getKeyFunction()

Gets the function that creates a "key object" for use as the grouping key.

Returns:

the function that creates a "key object" for use as the grouping key.

keyFunction

public GroupOperation<T> keyFunction(BsonJavaScript keyFunction)

Sets the function that creates a "key object" for use as the grouping key.

Parameters:

keyFunction - the function that creates a "key object" for use as the grouping key.

Returns:

this

getInitial

public BsonDocument getInitial()

Gets the initial the aggregation result document.

Returns:

the initial the aggregation result document.

getReduceFunction

public BsonJavaScript getReduceFunction()

Gets the aggregation function that operates on the documents during the grouping operation.

Returns:

the aggregation function that operates on the documents during the grouping operation.

getFilter

public BsonDocument getFilter()

Gets the query filter to determine which documents in the collection to process.

Returns:

the query filter to determine which documents in the collection to process.

filter

public GroupOperation<T> filter(BsonDocument filter)

Sets the optional query filter to determine which documents in the collection to process.

Parameters:

filter - the query filter to determine which documents in the collection to process.

Returns:

this

getFinalizeFunction

public BsonJavaScript getFinalizeFunction()

Gets the function that runs each item in the result before returning the final value.

Returns:

the function that runs each item in the result set before returning the final value.

finalizeFunction

public GroupOperation<T> finalizeFunction(BsonJavaScript finalizeFunction)

Sets the function that runs each item in the result set before returning the final value.

Parameters:

finalizeFunction - the function that runs each item in the result set before returning the final value.

Returns:

this

getCollation

public Collation getCollation()

Returns the collation options

Returns:

the collation options

Since:

3.4

Since server release

3.4

collation

public GroupOperation<T> collation(Collation collation)

Sets the collation options

A null value represents the server default.

Parameters:

collation - the collation options to use

Returns:

this

Since:

3.4

Since server release

3.4

execute

public BatchCursor<T> execute(ReadBinding binding)

Will return a cursor of Documents containing the results of the group operation.

Specified by:

execute in interface ReadOperation<T>

Parameters:

binding - the binding

Returns:

a MongoCursor of T, the results of the group operation in a form to be iterated over.

executeAsync

public void executeAsync(AsyncReadBinding binding,
                         SingleResultCallback<AsyncBatchCursor<T>> callback)

Description copied from interface: AsyncReadOperation

General execute which can return anything of type T

Specified by:

executeAsync in interface AsyncReadOperation<T>

Parameters:

binding - the binding to execute in the context of

callback - the callback to be called when the operation has been executed