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106 lines
3.3 KiB
C++
106 lines
3.3 KiB
C++
// shardkey.h
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/**
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* Copyright (C) 2008 10gen Inc.
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Affero General Public License, version 3,
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* as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Affero General Public License for more details.
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*
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* You should have received a copy of the GNU Affero General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#pragma once
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#include "../client/dbclient.h"
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namespace mongo {
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class Shard;
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/* A ShardKeyPattern is a pattern indicating what data to extract from the object to make the shard key from.
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Analogous to an index key pattern.
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*/
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class ShardKeyPattern {
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public:
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ShardKeyPattern( BSONObj fieldsAndOrder = emptyObj );
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/**
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global min is the lowest possible value for this key
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*/
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void globalMin( BSONObjBuilder & b );
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BSONObj globalMin(){ BSONObjBuilder b; globalMin( b ); return b.obj(); }
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/**
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global max is the lowest possible value for this key
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*/
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void globalMax( BSONObjBuilder & b );
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BSONObj globalMax(){ BSONObjBuilder b; globalMax( b ); return b.obj(); }
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/**
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return the key central between min and max
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note: min and max could cross type boundaries
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*/
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void middle( BSONObjBuilder & b , BSONObj & min , BSONObj & max );
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BSONObj middle( BSONObj & min , BSONObj & max ){ BSONObjBuilder b; middle( b , min , max ); return b.obj(); }
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/** compare shard keys from the objects specified
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l < r negative
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l == r 0
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l > r positive
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*/
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int compare( const BSONObj& l , const BSONObj& r ) const;
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/**
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* @return whether or not obj has all fields in this shard key pattern
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*/
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bool hasShardKey( const BSONObj& obj );
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/**
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returns a query that filters results only for the range desired, i.e. returns
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{ $gte : keyval(min), $lt : keyval(max) }
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*/
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void getFilter( BSONObjBuilder& b , const BSONObj& min, const BSONObj& max );
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/** @return true if shard s is relevant for query q.
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Example:
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q: { x : 3 }
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*this: { x : 1 }
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s: x:2..x:7
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-> true
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*/
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bool relevantForQuery( const BSONObj& q , Shard * s );
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//int ___numFields() const{ return _fieldsAndOrder.nFields(); }
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/**
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Example
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sort: { ts: -1 }
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*this: { ts:1 }
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-> -1
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@return
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0 if sort either doesn't have all the fields or has extra fields
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< 0 if sort is descending
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> 1 if sort is ascending
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*/
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int canOrder( const BSONObj& sort );
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BSONObj key() { return _fieldsAndOrder; }
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string toString() const;
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private:
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void _init();
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BSONObj _fieldsAndOrder;
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string _fieldName;
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};
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}
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