com.mongodb.operation

类 GroupOperation<T>

java.lang.Object

com.mongodb.operation.GroupOperation<T>

类型参数:

T - the operations result type.

所有已实现的接口:

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

public class GroupOperation<T>
extends java.lang.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.

从以下版本开始:

3.0

MongoDB documentation

Group Command

构造器概要

构造器

构造器和说明
GroupOperation(MongoNamespace namespace, BsonJavaScript reduceFunction, BsonDocument initial, Decoder<T> decoder) Create an operation that will perform a Group on a given collection.

方法概要

限定符和类型	方法和说明
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.
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.
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.

从类继承的方法 java.lang.Object

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

构造器详细资料

GroupOperation

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

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

参数:

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

方法详细资料

getKey

public BsonDocument getKey()

Gets the document containing the field or fields to group.

返回:

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.

参数:

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

返回:

this

getKeyFunction

public BsonJavaScript getKeyFunction()

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

返回:

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.

参数:

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

返回:

this

getInitial

public BsonDocument getInitial()

Gets the initial the aggregation result document.

返回:

the initial the aggregation result document.

getReduceFunction

public BsonJavaScript getReduceFunction()

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

返回:

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.

返回:

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.

参数:

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

返回:

this

getFinalizeFunction

public BsonJavaScript getFinalizeFunction()

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

返回:

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.

参数:

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

返回:

this

execute

public BatchCursor<T> execute(ReadBinding binding)

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

指定者:

execute 在接口中 ReadOperation<BatchCursor<T>>

参数:

binding - the binding

返回:

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)

从接口复制的说明: AsyncReadOperation

General execute which can return anything of type T

指定者:

executeAsync 在接口中 AsyncReadOperation<AsyncBatchCursor<T>>

参数:

binding - the binding to execute in the context of

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