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/**
* Copyright (C) 2013 10gen 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 <vector>
#include "mongo/db/diskloc.h"
#include "mongo/db/jsobj.h"
#include "mongo/platform/unordered_map.h"
namespace mongo {
struct WorkingSetMember;
typedef long WorkingSetID;
/**
* All data in use by a query. Data is passed through the stage tree by referencing the ID of
* an element of the working set. Stages can add elements to the working set, delete elements
* from the working set, or mutate elements in the working set.
*/
class WorkingSet {
public:
static const WorkingSetID INVALID_ID;
WorkingSet();
~WorkingSet();
/**
* Allocate a new query result and return the ID used to get and free it.
*/
WorkingSetID allocate();
/**
* Get the i-th mutable query result.
*/
WorkingSetMember* get(const WorkingSetID& i);
/**
* Unallocate the i-th query result and release its resouces.
*/
void free(const WorkingSetID& i);
/**
* The DiskLoc in WSM 'i' was invalidated while being processed. Any predicates over the
* WSM could not be fully evaluated, so the WSM may or may not satisfy them. As such, if we
* wish to output the WSM, we must do some clean-up work later. Adds the WSM with id 'i' to
* the list of flagged WSIDs.
*
* The WSM must be in the state OWNED_OBJ.
*/
void flagForReview(const WorkingSetID& i);
/**
* Return a vector of all WSIDs passed to flagForReview.
*/
const vector<WorkingSetID>& getFlagged() const;
private:
typedef unordered_map<WorkingSetID, WorkingSetMember*> DataMap;
DataMap _data;
// The WorkingSetID returned by the next call to allocate(). Should refer to the next valid
// ID. IDs allocated contiguously. Should never point at an in-use ID.
WorkingSetID _nextId;
// All WSIDs invalidated during evaluation of a predicate (AND).
vector<WorkingSetID> _flagged;
};
/**
* The key data extracted from an index. Keeps track of both the key (currently a BSONObj) and
* the index that provided the key. The index key pattern is required to correctly interpret
* the key.
*/
struct IndexKeyDatum {
IndexKeyDatum(const BSONObj& keyPattern, const BSONObj& key) : indexKeyPattern(keyPattern),
keyData(key) { }
// This is not owned and points into the IndexDescriptor's data.
BSONObj indexKeyPattern;
// This is the BSONObj for the key that we put into the index. Owned by us.
BSONObj keyData;
};
/**
* The type of the data passed between query stages. In particular:
*
* Index scan stages return a WorkingSetMember in the LOC_AND_IDX state.
*
* Collection scan stages the LOC_AND_UNOWNED_OBJ state.
*
* A WorkingSetMember may have any of the data above.
*/
struct WorkingSetMember {
WorkingSetMember();
enum MemberState {
// Initial state.
INVALID,
// Data is from 1 or more indices.
LOC_AND_IDX,
// Data is from a collection scan, or data is from an index scan and was fetched.
LOC_AND_UNOWNED_OBJ,
// DiskLoc has been invalidated, or the obj doesn't correspond to an on-disk document
// anymore (e.g. is a computed expression).
OWNED_OBJ,
};
DiskLoc loc;
BSONObj obj;
vector<IndexKeyDatum> keyData;
MemberState state;
bool hasLoc() const;
bool hasObj() const;
bool hasOwnedObj() const;
bool hasUnownedObj() const;
/**
* getFieldDotted uses its state (obj or index data) to produce the field with the provided
* name.
*
* Returns true if there is the element is in an index key or in an (owned or unowned)
* object. *out is set to the element if so.
*
* Returns false otherwise. Returning false indicates a query planning error.
*/
bool getFieldDotted(const string& field, BSONElement* out) const;
};
} // namespace mongo
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