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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 <memory>
#include "mongo/db/exec/inclusion_projection_executor.h"
#include "mongo/db/pipeline/expression.h"
#include "mongo/db/pipeline/expression_context.h"
namespace mongo::projection_executor {
/**
* A AddFieldsProjectionExecutor represents a projection execution tree for the $addFields stage.
*
* This class is mostly a wrapper around an InclusionNode tree. It contains logic to parse a
* specification object into the corresponding InclusionNode tree, but defers most execution logic
* to the underlying tree. In this way it is similar to InclusionProjectionExecutor, but it differs
* by not applying inclusions before adding computed fields, thus keeping all existing fields.
*/
class AddFieldsProjectionExecutor : public ProjectionExecutor {
public:
/**
* TODO SERVER-25510: The ProjectionExecutor _id and array-recursion policies are not
* applicable to the $addFields "projection" stage. We make them non-configurable here.
*/
AddFieldsProjectionExecutor(const boost::intrusive_ptr<ExpressionContext>& expCtx)
: ProjectionExecutor(expCtx,
{ProjectionPolicies::DefaultIdPolicy::kIncludeId,
ProjectionPolicies::ArrayRecursionPolicy::kRecurseNestedArrays,
ProjectionPolicies::ComputedFieldsPolicy::kAllowComputedFields}),
_root(new InclusionNode(_policies, true)) {}
/**
* Creates the data needed to perform an AddFields.
* Verifies that there are no conflicting paths in the specification.
*/
static std::unique_ptr<AddFieldsProjectionExecutor> create(
const boost::intrusive_ptr<ExpressionContext>& expCtx, const BSONObj& spec);
TransformerType getType() const final {
return TransformerType::kComputedProjection;
}
const InclusionNode& getRoot() const {
return *_root;
}
/**
* Parses the addFields specification given by 'spec', populating internal data structures.
*/
void parse(const BSONObj& spec);
Document serializeTransformation(
boost::optional<ExplainOptions::Verbosity> explain) const final {
return _root->serialize(explain);
}
/**
* Optimizes any computed expressions.
*/
void optimize() final {
_root->optimize();
}
DepsTracker::State addDependencies(DepsTracker* deps) const final {
_root->reportDependencies(deps);
return DepsTracker::State::SEE_NEXT;
}
DocumentSource::GetModPathsReturn getModifiedPaths() const final {
std::set<std::string> computedPaths;
StringMap<std::string> renamedPaths;
_root->reportComputedPaths(&computedPaths, &renamedPaths);
return {DocumentSource::GetModPathsReturn::Type::kFiniteSet,
std::move(computedPaths),
std::move(renamedPaths)};
}
/**
* Add the specified fields to 'inputDoc'.
*
* Replaced fields will remain in their original place in the document, while new added fields
* will be added to the end of the document in the order in which they were specified to the
* $addFields stage.
*
* Arrays will be traversed, with any dotted/nested computed fields applied to each element in
* the array. For example, setting "a.0": "hello" will add a field "0" to every object
* in the array "a". If there is an element in "a" that is not an object, it will be replaced
* with {"0": "hello"}. See SERVER-25200 for more details.
*/
Document applyProjection(const Document& inputDoc) const final;
boost::optional<std::set<FieldRef>> extractExhaustivePaths() const {
return boost::none;
}
private:
/**
* Attempts to parse 'objSpec' as an expression like {$add: [...]}. Adds a computed field to
* '_root' and returns true if it was successfully parsed as an expression. Returns false if it
* was not an expression specification.
*
* Throws an error if it was determined to be an expression specification, but failed to parse
* as a valid expression.
*/
bool parseObjectAsExpression(StringData pathToObject,
const BSONObj& objSpec,
const VariablesParseState& variablesParseState);
/**
* Traverses 'subObj' and parses each field. Adds any computed fields at this level
* to 'node'.
*/
void parseSubObject(const BSONObj& subObj,
const VariablesParseState& variablesParseState,
InclusionNode* node);
// The InclusionNode tree does most of the execution work once constructed.
std::unique_ptr<InclusionNode> _root;
};
} // namespace mongo::projection_executor
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