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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/pipeline/expression.h"
#include "mongo/db/pipeline/expression_context.h"
#include "mongo/db/pipeline/parsed_aggregation_projection.h"
#include "mongo/db/pipeline/parsed_aggregation_projection_node.h"
#include "mongo/stdx/unordered_map.h"
#include "mongo/stdx/unordered_set.h"
namespace mongo {
class FieldPath;
class Value;
namespace parsed_aggregation_projection {
/**
* A node used to define the parsed structure of an inclusion projection. Each InclusionNode
* represents one 'level' of the parsed specification. The root InclusionNode represents all top
* level inclusions or additions, with any child InclusionNodes representing dotted or nested
* inclusions or additions.
*/
class InclusionNode final : public ProjectionNode {
public:
InclusionNode(ProjectionPolicies policies, std::string pathToNode = "");
InclusionNode* addOrGetChild(const std::string& field);
void reportDependencies(DepsTracker* deps) const final;
protected:
// For inclusions, we can apply an optimization here by simply appending to the output document
// via MutableDocument::addField, rather than always checking for existing fields via setField.
void outputProjectedField(StringData field, Value val, MutableDocument* outputDoc) const final {
outputDoc->addField(field, val);
}
std::unique_ptr<ProjectionNode> makeChild(std::string fieldName) const final {
return std::make_unique<InclusionNode>(
_policies, FieldPath::getFullyQualifiedPath(_pathToNode, fieldName));
}
Document initializeOutputDocument(const Document& inputDoc) const final {
return {};
}
Value applyLeafProjectionToValue(const Value& value) const final {
return value;
}
Value transformSkippedValueForOutput(const Value& value) const final {
return Value();
}
};
/**
* A ParsedInclusionProjection represents a parsed form of the raw BSON specification.
*
* 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.
*/
class ParsedInclusionProjection : public ParsedAggregationProjection {
public:
ParsedInclusionProjection(const boost::intrusive_ptr<ExpressionContext>& expCtx,
ProjectionPolicies policies)
: ParsedAggregationProjection(expCtx, policies), _root(new InclusionNode(policies)) {}
TransformerType getType() const final {
return TransformerType::kInclusionProjection;
}
const InclusionNode& getRoot() const {
return *_root;
}
/**
* Parses the projection specification given by 'spec', populating internal data structures.
*/
void parse(const BSONObj& spec) final;
/**
* Serialize the projection.
*/
Document serializeTransformation(
boost::optional<ExplainOptions::Verbosity> explain) const final {
MutableDocument output;
if (_idExcluded) {
output.addField("_id", Value(false));
}
_root->serialize(explain, &output);
return output.freeze();
}
/**
* Optimize any computed expressions.
*/
void optimize() final {
_root->optimize();
}
DepsTracker::State addDependencies(DepsTracker* deps) const final {
_root->reportDependencies(deps);
return DepsTracker::State::EXHAUSTIVE_FIELDS;
}
DocumentSource::GetModPathsReturn getModifiedPaths() const final {
std::set<std::string> preservedPaths;
_root->reportProjectedPaths(&preservedPaths);
std::set<std::string> computedPaths;
StringMap<std::string> renamedPaths;
_root->reportComputedPaths(&computedPaths, &renamedPaths);
return {DocumentSource::GetModPathsReturn::Type::kAllExcept,
std::move(preservedPaths),
std::move(renamedPaths)};
}
/**
* Apply this exclusion projection to 'inputDoc'.
*
* All inclusions are processed before all computed fields. Computed fields will be added
* afterwards in the order in which they were specified to the $project stage.
*
* Arrays will be traversed, with any dotted/nested exclusions or computed fields applied to
* each element in the array.
*/
Document applyProjection(const Document& inputDoc) const final;
/*
* Checks whether the inclusion projection represented by the InclusionNode
* tree is a subset of the object passed in. Projections that have any
* computed or renamed fields are not considered a subset.
*/
bool isSubsetOfProjection(const BSONObj& proj) const final;
private:
/**
* Attempts to parse 'objSpec' as an expression like {$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 included or computed fields at this level
* to 'node'.
*/
void parseSubObject(const BSONObj& subObj,
const VariablesParseState& variablesParseState,
InclusionNode* node);
// Not strictly necessary to track here, but makes serialization easier.
bool _idExcluded = false;
// The InclusionNode tree does most of the execution work once constructed.
std::unique_ptr<InclusionNode> _root;
};
} // namespace parsed_aggregation_projection
} // namespace mongo
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