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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 "mongo/db/exec/working_set.h"
#include "mongo/db/jsobj.h"
#include "mongo/db/matcher/expression.h"
#include "mongo/db/matcher/expression_parser.h"
#include "mongo/util/string_map.h"
namespace mongo {
class ProjectionExec {
public:
/**
* A .find() projection can have an array operation, either an elemMatch or positional (or
* neither).
*/
enum ArrayOpType {
ARRAY_OP_NORMAL = 0,
ARRAY_OP_ELEM_MATCH,
ARRAY_OP_POSITIONAL
};
/**
* Projections based on data computed while answering a query, or other metadata about a
* document / query.
*/
enum MetaProjection {
META_TEXT_SCORE,
META_GEONEAR_DIST,
META_GEONEAR_POINT,
META_DISKLOC,
META_IX_KEY,
};
/**
* TODO: document why we like StringMap so much here
*/
typedef StringMap<ProjectionExec*> FieldMap;
typedef StringMap<MatchExpression*> Matchers;
typedef StringMap<MetaProjection> MetaMap;
ProjectionExec(const BSONObj& spec,
const MatchExpression* queryExpression,
const MatchExpressionParser::WhereCallback& whereCallback =
MatchExpressionParser::WhereCallback());
~ProjectionExec();
/**
* Apply this projection to the 'member'. Changes the type to OWNED_OBJ.
*/
Status transform(WorkingSetMember* member) const;
/**
* Apply this projection to the object 'in'.
*
* Upon success, 'out' is set to the new object and Status::OK() is returned.
* Otherwise, returns an error Status and *out is not mutated.
*/
Status transform(const BSONObj& in, BSONObj* out) const;
private:
//
// Initialization
//
ProjectionExec();
/**
* Add 'field' as a field name that is included or excluded as part of the projection.
*/
void add(const std::string& field, bool include);
/**
* Add 'field' as a field name that is sliced as part of the projection.
*/
void add(const std::string& field, int skip, int limit);
//
// Execution
//
/**
* Apply the projection that 'this' represents to the object 'in'. 'details' is the result
* of a match evaluation of the full query on the object 'in'. This is only required
* if the projection is positional.
*
* If the projection is successfully computed, returns Status::OK() and stuff the result in
* 'bob'.
* Otherwise, returns error.
*/
Status transform(const BSONObj& in,
BSONObjBuilder* bob,
const MatchDetails* details = NULL) const;
/**
* See transform(...) above.
*/
bool transformRequiresDetails() const {
return ARRAY_OP_POSITIONAL == _arrayOpType;
}
/**
* Is the full document required to compute this projection?
*/
bool requiresDocument() const {
return _include || _hasNonSimple || _hasDottedField;
}
/**
* Appends the element 'e' to the builder 'bob', possibly descending into sub-fields of 'e'
* if needed.
*/
Status append(BSONObjBuilder* bob,
const BSONElement& elt,
const MatchDetails* details = NULL,
const ArrayOpType arrayOpType = ARRAY_OP_NORMAL) const;
/**
* Like append, but for arrays.
* Deals with slice and calls appendArray to preserve the array-ness.
*/
void appendArray(BSONObjBuilder* bob, const BSONObj& array, bool nested = false) const;
// True if default at this level is to include.
bool _include;
// True if this level can't be skipped or included without recursing.
bool _special;
// We must group projections with common prefixes together.
// TODO: benchmark std::vector<pair> vs map
//
// Projection is a rooted tree. If we have {a.b: 1, a.c: 1} we don't want to
// double-traverse the document when we're projecting it. Instead, we have an entry in
// _fields for 'a' with two sub projections: b:1 and c:1.
FieldMap _fields;
// The raw projection spec. that is passed into init(...)
BSONObj _source;
// Should we include the _id field?
bool _includeID;
// Arguments from the $slice operator.
int _skip;
int _limit;
// Used for $elemMatch and positional operator ($)
Matchers _matchers;
// The matchers above point into BSONObjs and this is where those objs live.
std::vector<BSONObj> _elemMatchObjs;
ArrayOpType _arrayOpType;
// Is there an slice, elemMatch or meta operator?
bool _hasNonSimple;
// Is there a projection over a dotted field or a $ positional operator?
bool _hasDottedField;
// The full query expression. Used when we need MatchDetails.
const MatchExpression* _queryExpression;
// Projections that aren't sourced from the document or index keys.
MetaMap _meta;
// Do we have a returnKey projection? If so we *only* output the index key metadata. If
// it's not found we output nothing.
bool _hasReturnKey;
};
} // namespace mongo
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