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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 {
class FieldRangeSet;
/**
* 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:
QueryPattern( const FieldRangeSet &frs, const BSONObj &sort );
enum Type {
Empty,
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;
/** for development / debugging */
string toString() const;
private:
void setSort( const BSONObj sort );
static BSONObj normalizeSort( const BSONObj &spec );
map<string,Type> _fieldTypes;
BSONObj _sort;
};
/** Summarizes the candidate plans that may run for a query. */
class CandidatePlanCharacter {
public:
CandidatePlanCharacter( bool mayRunInOrderPlan, bool mayRunOutOfOrderPlan ) :
_mayRunInOrderPlan( mayRunInOrderPlan ),
_mayRunOutOfOrderPlan( mayRunOutOfOrderPlan ) {
}
CandidatePlanCharacter() :
_mayRunInOrderPlan(),
_mayRunOutOfOrderPlan() {
}
bool mayRunInOrderPlan() const { return _mayRunInOrderPlan; }
bool mayRunOutOfOrderPlan() const { return _mayRunOutOfOrderPlan; }
bool valid() const { return mayRunInOrderPlan() || mayRunOutOfOrderPlan(); }
bool hybridPlanSet() const { return mayRunInOrderPlan() && mayRunOutOfOrderPlan(); }
private:
bool _mayRunInOrderPlan;
bool _mayRunOutOfOrderPlan;
};
/** Information about a query plan that ran successfully for a QueryPattern. */
class CachedQueryPlan {
public:
CachedQueryPlan() :
_nScanned() {
}
CachedQueryPlan( const BSONObj &indexKey, long long nScanned,
CandidatePlanCharacter planCharacter );
BSONObj indexKey() const { return _indexKey; }
long long nScanned() const { return _nScanned; }
CandidatePlanCharacter planCharacter() const { return _planCharacter; }
private:
BSONObj _indexKey;
long long _nScanned;
CandidatePlanCharacter _planCharacter;
};
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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