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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.
*/
#define MONGO_LOG_DEFAULT_COMPONENT ::mongo::logger::LogComponent::kQuery
#include "mongo/platform/basic.h"
#include "mongo/db/matcher/rewrite_expr.h"
#include "mongo/db/matcher/expression_internal_expr_eq.h"
#include "mongo/db/matcher/expression_leaf.h"
#include "mongo/db/matcher/expression_tree.h"
#include "mongo/util/log.h"
namespace mongo {
using CmpOp = ExpressionCompare::CmpOp;
RewriteExpr::RewriteResult RewriteExpr::rewrite(const boost::intrusive_ptr<Expression>& expression,
const CollatorInterface* collator) {
LOG(5) << "Expression prior to rewrite: " << expression->serialize(false);
RewriteExpr rewriteExpr(collator);
std::unique_ptr<MatchExpression> matchExpression;
if (auto matchTree = rewriteExpr._rewriteExpression(expression)) {
matchExpression = std::move(matchTree);
LOG(5) << "Post-rewrite MatchExpression: " << matchExpression->debugString();
matchExpression = MatchExpression::optimize(std::move(matchExpression));
LOG(5) << "Post-rewrite/post-optimized MatchExpression: " << matchExpression->debugString();
}
return {std::move(matchExpression), std::move(rewriteExpr._matchExprElemStorage)};
}
std::unique_ptr<MatchExpression> RewriteExpr::_rewriteExpression(
const boost::intrusive_ptr<Expression>& currExprNode) {
if (auto expr = dynamic_cast<ExpressionAnd*>(currExprNode.get())) {
return _rewriteAndExpression(expr);
} else if (auto expr = dynamic_cast<ExpressionOr*>(currExprNode.get())) {
return _rewriteOrExpression(expr);
} else if (auto expr = dynamic_cast<ExpressionCompare*>(currExprNode.get())) {
return _rewriteComparisonExpression(expr);
}
return nullptr;
}
std::unique_ptr<MatchExpression> RewriteExpr::_rewriteAndExpression(
const boost::intrusive_ptr<ExpressionAnd>& currExprNode) {
auto andMatch = stdx::make_unique<AndMatchExpression>();
for (auto&& child : currExprNode->getOperandList()) {
if (auto childMatch = _rewriteExpression(child)) {
andMatch->add(childMatch.release());
}
}
if (andMatch->numChildren() > 0) {
return std::move(andMatch);
}
return nullptr;
}
std::unique_ptr<MatchExpression> RewriteExpr::_rewriteOrExpression(
const boost::intrusive_ptr<ExpressionOr>& currExprNode) {
auto orMatch = stdx::make_unique<OrMatchExpression>();
for (auto&& child : currExprNode->getOperandList()) {
if (auto childExpr = _rewriteExpression(child)) {
orMatch->add(childExpr.release());
} else {
// If any child cannot be rewritten to a MatchExpression then we must abandon adding
// this $or clause.
return nullptr;
}
}
if (orMatch->numChildren() > 0) {
return std::move(orMatch);
}
return nullptr;
}
std::unique_ptr<MatchExpression> RewriteExpr::_rewriteComparisonExpression(
const boost::intrusive_ptr<ExpressionCompare>& expr) {
if (!_canRewriteComparison(expr)) {
return nullptr;
}
const auto& operandList = expr->getOperandList();
invariant(operandList.size() == 2);
ExpressionFieldPath* lhs{nullptr};
ExpressionConstant* rhs{nullptr};
CmpOp cmpOperator = expr->getOp();
// Extract left-hand side and right-hand side MatchExpression components.
if ((lhs = dynamic_cast<ExpressionFieldPath*>(operandList[0].get()))) {
rhs = dynamic_cast<ExpressionConstant*>(operandList[1].get());
invariant(rhs);
} else {
lhs = dynamic_cast<ExpressionFieldPath*>(operandList[1].get());
rhs = dynamic_cast<ExpressionConstant*>(operandList[0].get());
invariant(lhs && rhs);
}
// Build argument for ComparisonMatchExpression.
const auto fieldPath = lhs->getFieldPath().tail();
BSONObjBuilder bob;
bob << fieldPath.fullPath() << rhs->getValue();
auto cmpObj = bob.obj();
_matchExprElemStorage.push_back(cmpObj);
return _buildComparisonMatchExpression(cmpOperator, cmpObj.firstElement());
}
std::unique_ptr<MatchExpression> RewriteExpr::_buildComparisonMatchExpression(
ExpressionCompare::CmpOp comparisonOp, BSONElement fieldAndValue) {
invariant(comparisonOp == ExpressionCompare::EQ);
auto eqMatchExpr =
stdx::make_unique<InternalExprEqMatchExpression>(fieldAndValue.fieldName(), fieldAndValue);
eqMatchExpr->setCollator(_collator);
return std::move(eqMatchExpr);
}
bool RewriteExpr::_canRewriteComparison(
const boost::intrusive_ptr<ExpressionCompare>& expression) const {
// Currently we only rewrite $eq expressions.
if (expression->getOp() != ExpressionCompare::EQ) {
return false;
}
const auto& operandList = expression->getOperandList();
bool hasFieldPath = false;
for (auto operand : operandList) {
if (auto exprFieldPath = dynamic_cast<ExpressionFieldPath*>(operand.get())) {
if (!exprFieldPath->isRootFieldPath()) {
// This field path refers to a variable rather than a local document field path.
return false;
}
if (hasFieldPath) {
// Match does not allow for more than one local document field path.
return false;
}
hasFieldPath = true;
} else if (auto exprConst = dynamic_cast<ExpressionConstant*>(operand.get())) {
switch (exprConst->getValue().getType()) {
case BSONType::Array:
case BSONType::EOO:
case BSONType::Undefined:
return false;
default:
break;
}
} else {
return false;
}
}
return hasFieldPath;
}
} // namespace mongo
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