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/**
* Copyright (C) 2018-present MongoDB, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the Server Side Public License, version 1,
* as published by MongoDB, Inc.
*
* 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
* Server Side Public License for more details.
*
* You should have received a copy of the Server Side Public License
* along with this program. If not, see
* <http://www.mongodb.com/licensing/server-side-public-license>.
*
* 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 Server Side 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/projection_exec_agg.h"
#include "mongo/db/field_ref.h"
#include "mongo/db/query/collation/collator_interface.h"
namespace mongo {
/**
* This class is responsible for generating an aggregation projection based on the keyPattern and
* pathProjection specs, and for subsequently extracting the set of all path-value pairs for each
* document.
*/
class WildcardKeyGenerator {
public:
static constexpr StringData kSubtreeSuffix = ".$**"_sd;
/**
* Returns an owned ProjectionExecAgg identical to the one that WildcardKeyGenerator will use
* internally when generating the keys for the $** index, as defined by the 'keyPattern' and
* 'pathProjection' arguments.
*/
static std::unique_ptr<ProjectionExecAgg> createProjectionExec(BSONObj keyPattern,
BSONObj pathProjection);
WildcardKeyGenerator(BSONObj keyPattern,
BSONObj pathProjection,
const CollatorInterface* collator);
/**
* Returns a pointer to the key generator's underlying ProjectionExecAgg.
*/
const ProjectionExecAgg* getProjectionExec() const {
return _projExec.get();
}
/**
* Applies the appropriate Wildcard projection to the input doc, and then adds one key-value
* pair to the BSONObjSet 'keys' for each leaf node in the post-projection document:
* { '': 'path.to.field', '': <collation-aware-field-value> }
* Also adds one entry to 'multikeyPaths' for each array encountered in the post-projection
* document, in the following format:
* { '': 1, '': 'path.to.array' }
*/
void generateKeys(BSONObj inputDoc, BSONObjSet* keys, BSONObjSet* multikeyPaths) const;
private:
// Traverses every path of the post-projection document, adding keys to the set as it goes.
void _traverseWildcard(BSONObj obj,
bool objIsArray,
FieldRef* path,
BSONObjSet* keys,
BSONObjSet* multikeyPaths) const;
// Helper functions to format the entry appropriately before adding it to the key/path tracker.
void _addMultiKey(const FieldRef& fullPath, BSONObjSet* multikeyPaths) const;
void _addKey(BSONElement elem, const FieldRef& fullPath, BSONObjSet* keys) const;
// Helper to check whether the element is a nested array, and conditionally add it to 'keys'.
bool _addKeyForNestedArray(BSONElement elem,
const FieldRef& fullPath,
bool enclosingObjIsArray,
BSONObjSet* keys) const;
bool _addKeyForEmptyLeaf(BSONElement elem, const FieldRef& fullPath, BSONObjSet* keys) const;
std::unique_ptr<ProjectionExecAgg> _projExec;
const CollatorInterface* _collator;
const BSONObj _keyPattern;
};
} // namespace mongo
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