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/**
* Copyright (C) 2019-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.
*/
#include "mongo/platform/basic.h"
#include "mongo/db/query/projection_ast_path_tracking_visitor.h"
#include "mongo/db/query/projection_ast_util.h"
#include "mongo/db/query/serialization_options.h"
#include "mongo/db/query/tree_walker.h"
namespace mongo::projection_ast {
namespace {
struct BSONVisitorContext {
std::stack<BSONObjBuilder> builders;
bool underElemMatch = false;
};
class BSONPreVisitor : public ProjectionASTConstVisitor {
public:
using ProjectionASTConstVisitor::visit;
BSONPreVisitor(PathTrackingVisitorContext<BSONVisitorContext>* context,
const SerializationOptions& options)
: _context(context), _builders(context->data().builders), _options(options) {}
void visit(const ProjectionPathASTNode* node) override {
if (!node->parent()) {
// No root of the tree, thus this node has no field name.
_builders.push(BSONObjBuilder());
} else {
_builders.push(_builders.top().subobjStart(getFieldName()));
}
}
void visit(const ProjectionSliceASTNode* node) override {
BSONObjBuilder sub(_builders.top().subobjStart(getFieldName()));
if (node->skip()) {
if (_options.replacementForLiteralArgs) {
const auto rep = _options.replacementForLiteralArgs.value();
sub.appendArray("$slice", BSON_ARRAY(rep << rep));
} else {
sub.appendArray("$slice", BSON_ARRAY(*node->skip() << node->limit()));
}
} else {
if (_options.replacementForLiteralArgs) {
sub.append("$slice", _options.replacementForLiteralArgs.value());
} else {
sub.appendNumber("$slice", node->limit());
}
}
}
void visit(const ExpressionASTNode* node) override {
node->expression()->serialize(_options).addToBsonObj(&_builders.top(), getFieldName());
}
void visit(const BooleanConstantASTNode* node) override {
_builders.top().append(getFieldName(), node->value());
}
void visit(const ProjectionPositionalASTNode* node) override = 0;
void visit(const ProjectionElemMatchASTNode* node) override = 0;
void visit(const MatchExpressionASTNode* node) override = 0;
protected:
std::string getFieldName() {
return _options.serializeFieldPathFromString(_context->childPath());
}
PathTrackingVisitorContext<BSONVisitorContext>* _context;
std::stack<BSONObjBuilder>& _builders;
SerializationOptions _options;
};
class BSONPostVisitor : public ProjectionASTConstVisitor {
public:
using ProjectionASTConstVisitor::visit;
BSONPostVisitor(BSONVisitorContext* context) : _context(context) {}
void visit(const ProjectionPathASTNode* node) override {
// Don't pop the top builder.
if (node->parent()) {
// Pop the BSONObjBuilder that was added in the pre visitor.
_context->builders.pop();
}
}
void visit(const ProjectionSliceASTNode* node) override {}
void visit(const ExpressionASTNode* node) override {}
void visit(const BooleanConstantASTNode* node) override {}
void visit(const MatchExpressionASTNode* node) override {}
void visit(const ProjectionPositionalASTNode* node) override = 0;
void visit(const ProjectionElemMatchASTNode* node) override = 0;
protected:
BSONVisitorContext* _context;
};
class DebugPreVisitor : public BSONPreVisitor {
public:
using BSONPreVisitor::visit;
DebugPreVisitor(PathTrackingVisitorContext<BSONVisitorContext>* context)
: BSONPreVisitor(context, SerializationOptions{}) {}
void visit(const ProjectionPositionalASTNode* node) override {
// ProjectionPositional always has the original query's match expression node as its
// child. Serialize as: {"positional.projection.field.$": <original match expression>}.
_context->data().builders.push(_builders.top().subobjStart(getFieldName() + ".$"));
}
void visit(const ProjectionElemMatchASTNode* node) override {
// Defer to the child, match expression node.
}
void visit(const MatchExpressionASTNode* node) override {
static_cast<const MatchExpressionASTNode*>(node)->matchExpression()->serialize(
&_builders.top(), {});
}
};
class DebugPostVisitor : public BSONPostVisitor {
public:
using BSONPostVisitor::visit;
DebugPostVisitor(BSONVisitorContext* context) : BSONPostVisitor(context) {}
void visit(const ProjectionPositionalASTNode* node) override {
_context->builders.pop();
}
void visit(const ProjectionElemMatchASTNode* node) override {}
};
class SerializationPreVisitor : public BSONPreVisitor {
public:
using BSONPreVisitor::visit;
SerializationPreVisitor(PathTrackingVisitorContext<BSONVisitorContext>* context,
SerializationOptions options)
: BSONPreVisitor(context, options) {}
void visit(const ProjectionPositionalASTNode* node) override {
tassert(73488,
"Positional projection should not appear below an $elemMatch projection.",
!_context->data().underElemMatch);
_builders.top().append(getFieldName() + ".$", true);
}
void visit(const ProjectionElemMatchASTNode* node) override {
// The child match expression node should begin with $elemMatch.
_context->data().underElemMatch = true;
}
void visit(const MatchExpressionASTNode* node) override {
if (_context->data().underElemMatch) {
static_cast<const MatchExpressionASTNode*>(node)->matchExpression()->serialize(
&_builders.top(), _options);
}
}
};
class SerializationPostVisitor : public BSONPostVisitor {
public:
using BSONPostVisitor::visit;
SerializationPostVisitor(BSONVisitorContext* context) : BSONPostVisitor(context) {}
void visit(const ProjectionPositionalASTNode* node) override {}
void visit(const ProjectionElemMatchASTNode* node) override {
_context->underElemMatch = false;
}
};
} // namespace
BSONObj astToDebugBSON(const ASTNode* root) {
PathTrackingVisitorContext<BSONVisitorContext> context;
DebugPreVisitor preVisitor{&context};
DebugPostVisitor postVisitor{&context.data()};
PathTrackingWalker walker{&context, {&preVisitor}, {&postVisitor}};
tree_walker::walk<true, projection_ast::ASTNode>(root, &walker);
invariant(context.data().builders.size() == 1);
return context.data().builders.top().obj();
}
BSONObj serialize(const ProjectionPathASTNode& root, SerializationOptions options) {
PathTrackingVisitorContext<BSONVisitorContext> context;
SerializationPreVisitor preVisitor{&context, options};
SerializationPostVisitor postVisitor{&context.data()};
PathTrackingWalker walker{&context, {&preVisitor}, {&postVisitor}};
tree_walker::walk<true, projection_ast::ASTNode>(&root, &walker);
invariant(context.data().builders.size() == 1);
return context.data().builders.top().obj();
}
} // namespace mongo::projection_ast
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