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/**
* Copyright (C) 2022-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 "query_rewriter.h"
#include "mongo/db/matcher/expression_expr.h"
#include "mongo/db/matcher/expression_parser.h"
#include "mongo/db/query/fle/range_validator.h"
namespace mongo::fle {
class ExpressionRewriter {
public:
ExpressionRewriter(QueryRewriter* queryRewriter, const ExpressionToRewriteMap& exprRewrites)
: queryRewriter(queryRewriter), exprRewrites(exprRewrites){};
std::unique_ptr<Expression> postVisit(Expression* exp) {
if (auto rewriteEntry = exprRewrites.find(typeid(*exp));
rewriteEntry != exprRewrites.end()) {
for (auto& rewrite : rewriteEntry->second) {
auto expr = rewrite(queryRewriter, exp);
if (expr != nullptr) {
didRewrite = true;
return expr;
}
}
}
return nullptr;
}
QueryRewriter* queryRewriter;
const ExpressionToRewriteMap& exprRewrites;
bool didRewrite = false;
};
std::unique_ptr<Expression> QueryRewriter::rewriteExpression(Expression* expression) {
tassert(6334104, "Expected an expression to rewrite but found none", expression);
ExpressionRewriter expressionRewriter{this, this->_exprRewrites};
auto res = expression_walker::walk<Expression>(expression, &expressionRewriter);
_rewroteLastExpression = expressionRewriter.didRewrite;
return res;
}
boost::optional<BSONObj> QueryRewriter::rewriteMatchExpression(const BSONObj& filter) {
auto expr = uassertStatusOK(MatchExpressionParser::parse(filter, _expCtx));
validateRanges(*expr.get());
_rewroteLastExpression = false;
if (auto res = _rewrite(expr.get())) {
// The rewrite resulted in top-level changes. Serialize the new expression.
return res->serialize().getOwned();
} else if (_rewroteLastExpression) {
// The rewrite had no top-level changes, but nested expressions were rewritten. Serialize
// the parsed expression, which has in-place changes.
return expr->serialize().getOwned();
}
// No rewrites were done.
return boost::none;
}
std::unique_ptr<MatchExpression> QueryRewriter::_rewrite(MatchExpression* expr) {
switch (expr->matchType()) {
case MatchExpression::AND:
case MatchExpression::OR:
case MatchExpression::NOT:
case MatchExpression::NOR: {
for (size_t i = 0; i < expr->numChildren(); i++) {
auto child = expr->getChild(i);
if (auto newChild = _rewrite(child)) {
expr->resetChild(i, newChild.release());
}
}
return nullptr;
}
case MatchExpression::EXPRESSION: {
// Save the current value of _rewroteLastExpression, since rewriteExpression() may
// reset it to false and we may have already done a match expression rewrite.
auto didRewrite = _rewroteLastExpression;
auto rewritten =
rewriteExpression(static_cast<ExprMatchExpression*>(expr)->getExpression().get());
_rewroteLastExpression |= didRewrite;
if (rewritten) {
return std::make_unique<ExprMatchExpression>(rewritten.release(),
getExpressionContext());
}
return nullptr;
}
default: {
if (auto rewriteEntry = _matchRewrites.find(expr->matchType());
rewriteEntry != _matchRewrites.end()) {
for (auto& rewrite : rewriteEntry->second) {
auto rewritten = rewrite(this, expr);
// Only one rewrite can be applied to an expression, so return as soon as a
// rewrite returns something other than nullptr.
if (rewritten != nullptr) {
_rewroteLastExpression = true;
return rewritten;
}
}
}
return nullptr;
}
}
}
} // namespace mongo::fle
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