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/**
* Copyright (C) 2012 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/>.
*
* 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 "mongo/base/string_data.h"
#include "mongo/db/jsobj.h"
namespace mongo {
/**
* A KeyPattern is an expression describing a transformation of a document into a
* document key. Document keys are used to store documents in indices and to target
* sharded queries.
*
* The root field names of KeyPatterns are always (potentially-dotted) paths, and the values of
* the fields describe the type of indexing over the found elements.
*
* Examples:
* { a : 1 }
* { a : 1 , b : -1 }
* { a : "hashed" }
*/
class KeyPattern {
public:
/**
* Is the provided key pattern the index over the ID field?
* The always required ID index is always {_id: 1} or {_id: -1}.
*/
static bool isIdKeyPattern(const BSONObj& pattern);
/**
* Is the provided key pattern ordered increasing or decreasing or not?
*/
static bool isOrderedKeyPattern(const BSONObj& pattern);
/**
* Does the provided key pattern hash its keys?
*/
static bool isHashedKeyPattern(const BSONObj& pattern);
/**
* Constructs a new key pattern based on a BSON document
*/
KeyPattern(const BSONObj& pattern);
/**
* Returns a BSON representation of this KeyPattern.
*/
const BSONObj& toBSON() const {
return _pattern;
}
/**
* Returns a string representation of this KeyPattern
*/
std::string toString() const {
return toBSON().toString();
}
/* Takes a BSONObj whose field names are a prefix of the fields in this keyPattern, and
* outputs a new bound with MinKey values appended to match the fields in this keyPattern
* (or MaxKey values for descending -1 fields). This is useful in sharding for
* calculating chunk boundaries when tag ranges are specified on a prefix of the actual
* shard key, or for calculating index bounds when the shard key is a prefix of the actual
* index used.
*
* @param makeUpperInclusive If true, then MaxKeys instead of MinKeys will be appended, so
* that the output bound will compare *greater* than the bound being extended (note that
* -1's in the keyPattern will swap MinKey/MaxKey vals. See examples).
*
* Examples:
* If this keyPattern is {a : 1}
* extendRangeBound( {a : 55}, false) --> {a : 55}
*
* If this keyPattern is {a : 1, b : 1}
* extendRangeBound( {a : 55}, false) --> {a : 55, b : MinKey}
* extendRangeBound( {a : 55}, true ) --> {a : 55, b : MaxKey}
*
* If this keyPattern is {a : 1, b : -1}
* extendRangeBound( {a : 55}, false) --> {a : 55, b : MaxKey}
* extendRangeBound( {a : 55}, true ) --> {a : 55, b : MinKey}
*/
BSONObj extendRangeBound(const BSONObj& bound, bool makeUpperInclusive) const;
BSONObj globalMin() const;
BSONObj globalMax() const;
private:
BSONObj _pattern;
};
} // namespace mongo
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