/**
* Copyright (C) 2017 MongoDB Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License, version 3,
* as published by the Free Software Foundation.
*
* 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
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see .
*
* 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 GNU Affero General 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
#include
#include "mongo/base/status_with.h"
#include "mongo/db/matcher/expression.h"
#include "mongo/db/pipeline/expression_context.h"
namespace mongo {
/**
* Container for a parsed MatchExpression and top-level field name that it's over.
* For example, {"i.a": 0, "i.b": 1} is a filter with a single top-level field name "i".
*/
class ExpressionWithPlaceholder {
public:
static const std::regex placeholderRegex;
/**
* Constructs an ExpressionWithPlaceholder from an existing match expression. Returns a non-OK
* status if the paths inside the match expression do not name a consistent placeholder string.
*/
static StatusWith> make(
std::unique_ptr filter);
/**
* Construct a new ExpressionWithPlaceholder. 'filter' must point to a valid MatchExpression.
*/
ExpressionWithPlaceholder(boost::optional placeholder,
std::unique_ptr filter)
: _placeholder(std::move(placeholder)), _filter(std::move(filter)) {
invariant(static_cast(_filter));
}
/**
* Returns true if this expression has both a placeholder and filter equivalent to 'other'.
*/
bool equivalent(const ExpressionWithPlaceholder* other) const;
/**
* Uses this filter to match against 'elem' as if it is wrapped in a BSONObj with a single
* field whose name is given by getPlaceholder(). If the placeholder name does not exist, then
* the filter expression does not refer to any specific paths.
*/
bool matchesBSONElement(BSONElement elem, MatchDetails* details = nullptr) const {
return _filter->matchesBSONElement(elem, details);
}
/**
* If this object has a placeholder, returns a view of the placeholder as a StringData.
*/
boost::optional getPlaceholder() const {
if (_placeholder) {
return StringData(*_placeholder);
}
return boost::none;
}
MatchExpression* getFilter() const {
return _filter.get();
}
std::unique_ptr shallowClone() const {
return stdx::make_unique(_placeholder, _filter->shallowClone());
}
/*
* Uses MatchExpression::optimize() to replace the Expression part of this
* ExpressionWithPlaceholder with an optimized expression. If the rewritten expression operates
* on a different field, we also update the placeholder to match.
*/
void optimizeFilter();
private:
// The top-level field that _filter is over.
boost::optional _placeholder;
std::unique_ptr _filter;
};
} // namespace mongo