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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.
*/
#include "mongo/db/matcher/expression_visitor.h"
#include "mongo/db/pipeline/expression.h"
#include "mongo/platform/basic.h"
#include "mongo/db/matcher/expression_expr.h"
#include "mongo/db/matcher/expression_internal_eq_hashed_key.h"
#include "mongo/util/fail_point.h"
namespace mongo {
MONGO_FAIL_POINT_DEFINE(ExprMatchExpressionMatchesReturnsFalseOnException);
ExprMatchExpression::ExprMatchExpression(boost::intrusive_ptr<Expression> expr,
const boost::intrusive_ptr<ExpressionContext>& expCtx,
clonable_ptr<ErrorAnnotation> annotation)
: MatchExpression(MatchType::EXPRESSION, std::move(annotation)),
_expCtx(expCtx),
_expression(expr) {}
ExprMatchExpression::ExprMatchExpression(BSONElement elem,
const boost::intrusive_ptr<ExpressionContext>& expCtx,
clonable_ptr<ErrorAnnotation> annotation)
: ExprMatchExpression(Expression::parseOperand(expCtx.get(), elem, expCtx->variablesParseState),
expCtx,
std::move(annotation)) {}
bool ExprMatchExpression::matches(const MatchableDocument* doc, MatchDetails* details) const {
if (_rewriteResult && _rewriteResult->matchExpression() &&
!_rewriteResult->matchExpression()->matches(doc, details)) {
return false;
}
try {
return evaluateExpression(doc).coerceToBool();
} catch (const DBException&) {
if (MONGO_unlikely(ExprMatchExpressionMatchesReturnsFalseOnException.shouldFail())) {
return false;
}
throw;
}
}
Value ExprMatchExpression::evaluateExpression(const MatchableDocument* doc) const {
Document document(doc->toBSON());
// 'Variables' is not thread safe, and ExprMatchExpression may be used in a validator which
// processes documents from multiple threads simultaneously. Hence we make a copy of the
// 'Variables' object per-caller.
Variables variables = _expCtx->variables;
return _expression->evaluate(document, &variables);
}
void ExprMatchExpression::serialize(BSONObjBuilder* out, SerializationOptions opts) const {
*out << "$expr" << _expression->serialize(opts);
}
bool ExprMatchExpression::equivalent(const MatchExpression* other) const {
if (other->matchType() != matchType()) {
return false;
}
const ExprMatchExpression* realOther = static_cast<const ExprMatchExpression*>(other);
if (!CollatorInterface::collatorsMatch(_expCtx->getCollator(),
realOther->_expCtx->getCollator())) {
return false;
}
// TODO SERVER-30982: Add mechanism to allow for checking Expression equivalency.
return ValueComparator().evaluate(_expression->serialize(false) ==
realOther->_expression->serialize(false));
}
void ExprMatchExpression::_doSetCollator(const CollatorInterface* collator) {
// This function is used to give match expression nodes which don't keep a pointer to the
// ExpressionContext access to the ExpressionContext's collator. Since the operation only ever
// has a single CollatorInterface, and since that collator is kept on the ExpressionContext,
// the collator pointer that we're propagating throughout the MatchExpression tree must match
// the one inside the ExpressionContext.
invariant(collator == _expCtx->getCollator());
if (_rewriteResult && _rewriteResult->matchExpression()) {
_rewriteResult->matchExpression()->setCollator(collator);
}
}
std::unique_ptr<MatchExpression> ExprMatchExpression::clone() const {
// TODO SERVER-31003: Replace Expression clone via serialization with Expression::clone().
BSONObjBuilder bob;
bob << "" << _expression->serialize(false);
boost::intrusive_ptr<Expression> clonedExpr = Expression::parseOperand(
_expCtx.get(), bob.obj().firstElement(), _expCtx->variablesParseState);
auto clone =
std::make_unique<ExprMatchExpression>(std::move(clonedExpr), _expCtx, _errorAnnotation);
if (_rewriteResult) {
clone->_rewriteResult = _rewriteResult->clone();
}
return clone;
}
bool ExprMatchExpression::isTriviallyTrue() const {
auto exprConst = dynamic_cast<ExpressionConstant*>(_expression.get());
return exprConst && exprConst->getValue().coerceToBool();
}
namespace {
// Return nullptr on failure.
std::unique_ptr<MatchExpression> attemptToRewriteEqHash(ExprMatchExpression& expr) {
auto childExpr = expr.getExpression();
// Looking for:
// $eq
// $toHashedIndexKey {$const: NumberLong(?)}
// "$a"
//
// Where "a" can be any field path and ? can be any number.
if (auto eq = dynamic_cast<ExpressionCompare*>(childExpr.get());
eq && eq->getOp() == ExpressionCompare::CmpOp::EQ) {
auto children = eq->getChildren();
tassert(7281406, "should have 2 $eq children", children.size() == 2ul);
auto eqFirst = children[0].get();
auto eqSecond = children[1].get();
if (auto hashingExpr = dynamic_cast<ExpressionToHashedIndexKey*>(eqFirst)) {
// Matched $toHashedIndexKey - keep going.
tassert(7281407,
"should have 1 $toHashedIndexKey child",
hashingExpr->getChildren().size() == 1ul);
auto hashChild = hashingExpr->getChildren()[0].get();
if (auto fieldPath = dynamic_cast<ExpressionFieldPath*>(hashChild);
fieldPath && !fieldPath->isVariableReference() && !fieldPath->isROOT()) {
auto path = fieldPath->getFieldPathWithoutCurrentPrefix();
// Matched "$a" in the example above! Now look for the constant long:
if (auto constant = dynamic_cast<ExpressionConstant*>(eqSecond);
constant && constant->getValue().getType() == BSONType::NumberLong) {
long long hashTarget = constant->getValue().getLong();
return std::make_unique<InternalEqHashedKey>(path.fullPath(), hashTarget);
}
}
}
}
return nullptr;
}
} // namespace
MatchExpression::ExpressionOptimizerFunc ExprMatchExpression::getOptimizer() const {
return [](std::unique_ptr<MatchExpression> expression) {
auto& exprMatchExpr = static_cast<ExprMatchExpression&>(*expression);
// If '_expression' can be rewritten to a MatchExpression, we will return a $and node with
// both the original ExprMatchExpression and the MatchExpression rewrite as children.
// Exiting early prevents additional calls to optimize from performing additional rewrites
// and adding duplicate MatchExpression sub-trees to the tree.
if (exprMatchExpr._rewriteResult) {
return expression;
}
exprMatchExpr._expression = exprMatchExpr._expression->optimize();
if (auto successfulEqHashRewrite = attemptToRewriteEqHash(exprMatchExpr)) {
return successfulEqHashRewrite;
}
exprMatchExpr._rewriteResult =
RewriteExpr::rewrite(exprMatchExpr._expression, exprMatchExpr._expCtx->getCollator());
if (exprMatchExpr._rewriteResult->matchExpression()) {
auto andMatch = std::make_unique<AndMatchExpression>();
andMatch->add(exprMatchExpr._rewriteResult->releaseMatchExpression());
andMatch->add(std::move(expression));
// Re-optimize the new AND in order to make sure that any AND children are absorbed.
expression = MatchExpression::optimize(std::move(andMatch));
}
// Replace trivially true expression with an empty AND since the planner doesn't always
// check for 'isTriviallyTrue()'.
if (expression->isTriviallyTrue()) {
expression = std::make_unique<AndMatchExpression>();
}
return expression;
};
}
} // namespace mongo
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