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/**
* Copyright (C) 2022-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/pipeline/field_path.h"
#include "mongo/db/query/optimizer/node.h"
namespace mongo::optimizer {
/**
* Represents a tree of paths with attached properties. For example adding "a.b" and "a.c" results
* in a root node "a" with two children "b" and "c". By setting appropriate properties we can create
* a path tree for a $project expression:
* Field "a" * Keep "a"
* |
* Traverse
* |
* Obj * Keep "b", "c"
*/
struct FieldMapEntry {
FieldMapEntry(FieldNameType fieldName) : _fieldName(std::move(fieldName)) {
uassert(6624200, "Empty field name", !_fieldName.value().empty());
}
FieldNameType _fieldName;
bool _hasKeep = false;
bool _hasLeadingObj = false;
bool _hasTrailingDefault = false;
bool _hasDrop = false;
boost::optional<ProjectionName> _constVarName;
// Child paths are potentially dotted field paths.
OrderedPathSet _childPaths;
};
class FieldMapBuilder {
static constexpr const char* kRootElement = "$root";
public:
FieldMapBuilder(const ProjectionName& rootProjName, bool isRootSameAsScanProj)
: _rootProjName(rootProjName), _isRootSameAsScanProj(isRootSameAsScanProj) {}
/**
* Adds 'fieldPath' as a projected field, creating FieldMapEntries for each element along the
* path as necessary, and applying 'fn' to each created FieldMapEntry.
*/
void integrateFieldPath(
const FieldPath& fieldPath,
const std::function<void(const bool isLastElement, FieldMapEntry& entry)>& fn);
/**
* Produce an ABT representing all fields integrated so far under a single EvalPath. For
* example, assuming "a.b" and "a.c" were integrated as fields in an inclusion projection, an
* output may look like:
* EvalPath
* | |
* Field "a" * Keep "a" Variable[rootProjName]
* |
* Traverse
* |
* Obj * Keep "b", "c"
*
* Returns boost::none when no fields have been integrated so far.
*/
boost::optional<ABT> generateABT() const;
private:
ABT generateABTForField(const FieldMapEntry& entry) const;
const ProjectionName& _rootProjName;
const bool _isRootSameAsScanProj;
// Maps from potentially dotted field path to FieldMapEntry.
opt::unordered_map<std::string, FieldMapEntry> _fieldMap;
};
} // namespace mongo::optimizer
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