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