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/**
* Copyright (C) 2014 MongoDB Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License, version 3,
* as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the GNU Affero General Public License in all respects for
* all of the code used other than as permitted herein. If you modify file(s)
* with this exception, you may extend this exception to your version of the
* file(s), but you are not obligated to do so. If you do not wish to do so,
* delete this exception statement from your version. If you delete this
* exception statement from all source files in the program, then also delete
* it in the license file.
*/
#pragma once
#include "mongo/bson/simple_bsonobj_comparator.h"
#include "mongo/db/exec/plan_stage.h"
#include "mongo/db/namespace_string.h"
#include "mongo/scripting/engine.h"
namespace mongo {
class Collection;
/**
* A description of a request for a group operation. Copyable.
*/
struct GroupRequest {
// Namespace to operate on (e.g. "foo.bar").
NamespaceString ns;
// A predicate describing the set of documents to group.
BSONObj query;
// The field(s) to group by. Alternative to "keyFunctionCode". Empty if "keyFunctionCode"
// is being used instead.
BSONObj keyPattern;
// A Javascript function that maps a document to a key object. Alternative to "keyPattern".
// Empty is "keyPattern" is being used instead.
std::string keyFunctionCode;
// The collation used for string comparisons. If empty, simple binary comparison with memcmp()
// is used.
BSONObj collation;
// A Javascript function that takes a (input document, group result) pair and
// updates the group result document.
std::string reduceCode;
// Scope for the reduce function. Optional.
BSONObj reduceScope;
// The initial value for the group result.
BSONObj initial;
// A Javascript function that "finalizes" a group result. Optional.
std::string finalize;
// Whether this is an explain of a group.
bool explain;
};
/**
* Stage used by the group command. Consumes input documents from its child stage (returning
* NEED_TIME once for each document produced by the child), returns ADVANCED exactly once with
* the entire group result, then returns EOF.
*
* Only created through the getExecutorGroup path.
*/
class GroupStage final : public PlanStage {
MONGO_DISALLOW_COPYING(GroupStage);
public:
GroupStage(OperationContext* txn,
const GroupRequest& request,
WorkingSet* workingSet,
PlanStage* child);
StageState doWork(WorkingSetID* out) final;
bool isEOF() final;
StageType stageType() const final {
return STAGE_GROUP;
}
std::unique_ptr<PlanStageStats> getStats() final;
const SpecificStats* getSpecificStats() const final;
static const char* kStageType;
private:
/**
* Keeps track of what this group is currently doing so that it can do the right thing on
* the next call to work().
*/
enum GroupState {
// Need to initialize the underlying Javascript machinery.
GroupState_Initializing,
// Retrieving the next document from the child stage and processing it.
GroupState_ReadingFromChild,
// Results have been returned.
GroupState_Done
};
// Initializes _scope, _reduceFunction and _keyFunction using the global scripting engine.
Status initGroupScripting();
// Updates _groupMap and _scope to account for the group key associated with this object.
// Returns an error status if an error occurred, else Status::OK().
Status processObject(const BSONObj& obj);
// Finalize the results for this group operation. On success, returns with a BSONObj with
// the results array. On failure, returns a non-OK status. Does not throw.
StatusWith<BSONObj> finalizeResults();
GroupRequest _request;
// The WorkingSet we annotate with results. Not owned by us.
WorkingSet* _ws;
GroupStats _specificStats;
// Current state for this stage.
GroupState _groupState;
// The Scope object that all script operations for this group stage will use. Initialized
// by initGroupScripting(). Owned here.
std::unique_ptr<Scope> _scope;
// The reduce function for the group operation. Initialized by initGroupScripting(). Owned
// by _scope.
ScriptingFunction _reduceFunction;
// The key function for the group operation if one was provided by the user, else 0.
// Initialized by initGroupScripting(). Owned by _scope.
ScriptingFunction _keyFunction;
// Map from group key => group index. The group index is used to index into "$arr", a
// variable owned by _scope which contains the group data for this key.
BSONObjIndexedMap<int> _groupMap;
};
} // namespace mongo
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