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diff --git a/src/mongo/db/querypattern.cpp b/src/mongo/db/querypattern.cpp
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+// @file querypattern.cpp - 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.
+ */
+
+#include "querypattern.h"
+#include "mongo/db/queryutil.h"
+
+namespace mongo {
+
+    QueryPattern::QueryPattern( const FieldRangeSet &frs, const BSONObj &sort ) {
+        for( map<string,FieldRange>::const_iterator i = frs.ranges().begin(); i != frs.ranges().end(); ++i ) {
+            if ( i->second.equality() ) {
+                _fieldTypes[ i->first ] = QueryPattern::Equality;
+            }
+            else if ( i->second.empty() ) {
+                _fieldTypes[ i->first ] = QueryPattern::Empty;
+            }
+            else if ( !i->second.universal() ) {
+                bool upper = i->second.max().type() != MaxKey;
+                bool lower = i->second.min().type() != MinKey;
+                if ( upper && lower ) {
+                    _fieldTypes[ i->first ] = QueryPattern::UpperAndLowerBound;
+                }
+                else if ( upper ) {
+                    _fieldTypes[ i->first ] = QueryPattern::UpperBound;
+                }
+                else if ( lower ) {
+                    _fieldTypes[ i->first ] = QueryPattern::LowerBound;
+                }
+                else {
+                    _fieldTypes[ i->first ] = QueryPattern::ConstraintPresent;
+                }
+            }
+        }
+        setSort( sort );
+    }
+
+    /** for testing only - speed unimportant */
+    bool QueryPattern::operator==( const QueryPattern &other ) const {
+        bool less = operator<( other );
+        bool more = other.operator<( *this );
+        verify( !( less && more ) );
+        return !( less || more );
+    }
+    
+    /** for testing only - speed unimportant */
+    bool QueryPattern::operator!=( const QueryPattern &other ) const {
+        return !operator==( other );
+    }
+    
+    string typeToString( enum QueryPattern::Type t ) {
+        switch (t) {
+            case QueryPattern::Empty:
+                return "Empty";
+            case QueryPattern::Equality:
+                return "Equality";
+            case QueryPattern::LowerBound:
+                return "LowerBound";
+            case QueryPattern::UpperBound:
+                return "UpperBound";
+            case QueryPattern::UpperAndLowerBound:
+                return "UpperAndLowerBound";
+            case QueryPattern::ConstraintPresent:
+                return "ConstraintPresent";
+        }
+        return "";
+    }
+    
+    string QueryPattern::toString() const {
+        BSONObjBuilder b;
+        for( map<string,Type>::const_iterator i = _fieldTypes.begin(); i != _fieldTypes.end(); ++i ) {
+            b << i->first << typeToString( i->second );
+        }
+        return BSON( "query" << b.done() << "sort" << _sort ).toString();
+    }
+    
+    void QueryPattern::setSort( const BSONObj sort ) {
+        _sort = normalizeSort( sort );
+    }
+    
+    BSONObj QueryPattern::normalizeSort( const BSONObj &spec ) {
+        if ( spec.isEmpty() )
+            return spec;
+        int direction = ( spec.firstElement().number() >= 0 ) ? 1 : -1;
+        BSONObjIterator i( spec );
+        BSONObjBuilder b;
+        while( i.moreWithEOO() ) {
+            BSONElement e = i.next();
+            if ( e.eoo() )
+                break;
+            b.append( e.fieldName(), direction * ( ( e.number() >= 0 ) ? -1 : 1 ) );
+        }
+        return b.obj();
+    }
+    
+    CachedQueryPlan::CachedQueryPlan( const BSONObj &indexKey, long long nScanned,
+                                     CandidatePlanCharacter planCharacter ) :
+    _indexKey( indexKey ),
+    _nScanned( nScanned ),
+    _planCharacter( planCharacter ) {
+    }
+
+    
+} // namespace mongo