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/**
* Copyright (C) 2013 10gen 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 <http://www.gnu.org/licenses/>.
*/
#pragma once
namespace mongo {
class BSONObj;
class FieldRangeSet;
enum IndexSuitability { USELESS = 0 , HELPFUL = 1 , OPTIMAL = 2 };
/**
* This class is part of query optimization. For a given index (as uniquely described by
* keyPattern) and a given query (queryConstraints) and given sort order (order), return how
* "suitable" the index is for the query + sort.
*
* USELESS indices are never used.
* HELPFUL indices are explored and compared to other HELPFUL indices.
* OPTIMAL indices short-circuit the search process and are always used.
*/
class IndexSelection {
public:
static IndexSuitability isSuitableFor(const BSONObj& keyPattern,
const FieldRangeSet& queryConstraints,
const BSONObj& order);
};
} // namespace mongo
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