// @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
        };
        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
