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// shardkey.h
/**
* Copyright (C) 2008 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
#include "../client/dbclient.h"
namespace mongo {
class Shard;
/* A ShardKeyPattern is a pattern indicating what data to extract from the object to make the shard key from.
Analogous to an index key pattern.
*/
class ShardKeyPattern {
public:
ShardKeyPattern( BSONObj p = BSONObj() ) : pattern( p.getOwned() ) {
pattern.getFieldNames(patternfields);
}
/**
global min is the lowest possible value for this key
e.g. { num : MinKey }
*/
BSONObj globalMin() const;
/**
global max is the lowest possible value for this key
*/
BSONObj globalMax() const;
bool isGlobalMin( const BSONObj& k ){
return k.woCompare( globalMin() ) == 0;
}
bool isGlobalMax( const BSONObj& k ){
return k.woCompare( globalMax() ) == 0;
}
bool isGlobal( const BSONObj& k ){
return isGlobalMin( k ) || isGlobalMax( k );
}
/** compare shard keys from the objects specified
l < r negative
l == r 0
l > r positive
*/
int compare( const BSONObj& l , const BSONObj& r );
/**
@return whether or not obj has all fields in this shard key pattern
e.g.
ShardKey({num:1}).hasShardKey({ name:"joe", num:3 }) is true
*/
bool hasShardKey( const BSONObj& obj );
/**
returns a query that filters results only for the range desired, i.e. returns
{ "field" : { $gte: keyval(min), $lt: keyval(max) } }
*/
void getFilter( BSONObjBuilder& b , const BSONObj& min, const BSONObj& max );
/** @return true if shard s is relevant for query q.
Example:
q: { x : 3 }
*this: { x : 1 }
s: x:2..x:7
-> true
*/
bool relevantForQuery( const BSONObj& q , Shard * s );
/**
Returns if the given sort pattern can be ordered by the shard key pattern.
Example
sort: { ts: -1 }
*this: { ts:1 }
-> -1
@return
0 if sort either doesn't have all the fields or has extra fields
< 0 if sort is descending
> 1 if sort is ascending
*/
int canOrder( const BSONObj& sort );
BSONObj key() { return pattern; }
string toString() const;
ShardKeyPattern(const ShardKeyPattern& p) {
pattern = p.pattern;
patternfields = p.patternfields;
}
BSONObj extractKey(const BSONObj& from) const;
private:
/* question: better to have patternfields precomputed or not? depends on if we use copy contructor often. */
BSONObj pattern;
set<string> patternfields;
bool relevant(const BSONObj& query, BSONObj& L, BSONObj& R);
};
inline BSONObj ShardKeyPattern::extractKey(const BSONObj& from) const {
return from.extractFields(pattern);
}
}
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