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// @file querypattern.h - Query pattern matching for selecting similar plans given similar queries.
/* Copyright 2011 10gen Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#pragma once
#include "jsobj.h"
namespace mongo {
/**
* Implements query pattern matching, used to determine if a query is
* similar to an earlier query and should use the same plan.
*
* Two queries will generate the same QueryPattern, and therefore match each
* other, if their fields have the same Types and they have the same sort
* spec.
*/
class QueryPattern {
public:
friend class FieldRangeSet;
enum Type {
Equality,
LowerBound,
UpperBound,
UpperAndLowerBound,
ConstraintPresent
};
bool operator<( const QueryPattern &other ) const;
/** for testing only */
bool operator==( const QueryPattern &other ) const;
/** for testing only */
bool operator!=( const QueryPattern &other ) const;
private:
QueryPattern() {}
void setSort( const BSONObj sort );
static BSONObj normalizeSort( const BSONObj &spec );
map<string,Type> _fieldTypes;
BSONObj _sort;
};
inline bool QueryPattern::operator<( const QueryPattern &other ) const {
map<string,Type>::const_iterator i = _fieldTypes.begin();
map<string,Type>::const_iterator j = other._fieldTypes.begin();
while( i != _fieldTypes.end() ) {
if ( j == other._fieldTypes.end() )
return false;
if ( i->first < j->first )
return true;
else if ( i->first > j->first )
return false;
if ( i->second < j->second )
return true;
else if ( i->second > j->second )
return false;
++i;
++j;
}
if ( j != other._fieldTypes.end() )
return true;
return _sort.woCompare( other._sort ) < 0;
}
} // namespace mongo
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