mongodb/db/queryutil.h

// @file queryutil.h - Utility classes representing ranges of valid BSONElement values for a query.

/*    Copyright 2009 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"
#include "indexkey.h"

namespace mongo {

    /**
     * One side of an interval of valid BSONElements, specified by a value and a
     * boolean indicating whether the interval includes the value.
     */
    struct FieldBound {
        BSONElement _bound;
        bool _inclusive;
        bool operator==( const FieldBound &other ) const {
            return _bound.woCompare( other._bound ) == 0 &&
                   _inclusive == other._inclusive;
        }
        void flipInclusive() { _inclusive = !_inclusive; }
    };

    /** A closed interval composed of a lower and an upper FieldBound. */
    struct FieldInterval {
        FieldInterval() : _cachedEquality( -1 ) {}
        FieldInterval( const BSONElement& e ) : _cachedEquality( -1 ) {
            _lower._bound = _upper._bound = e;
            _lower._inclusive = _upper._inclusive = true;
        }
        FieldBound _lower;
        FieldBound _upper;
        /** @return true iff no single element can be contained in the interval. */
        bool strictValid() const {
            int cmp = _lower._bound.woCompare( _upper._bound, false );
            return ( cmp < 0 || ( cmp == 0 && _lower._inclusive && _upper._inclusive ) );
        }
        /** @return true iff the interval is an equality constraint. */
        bool equality() const;
        mutable int _cachedEquality;
    };

    /**
     * An ordered list of FieldIntervals expressing constraints on valid
     * BSONElement values for a field.
     */
    class FieldRange {
    public:
        FieldRange( const BSONElement &e , bool singleKey , bool isNot=false , bool optimize=true );

        /** @return Range intersection with 'other'. */
        const FieldRange &operator&=( const FieldRange &other );
        /** @return Range union with 'other'. */
        const FieldRange &operator|=( const FieldRange &other );
        /** @return Range of elements elements included in 'this' but not 'other'. */
        const FieldRange &operator-=( const FieldRange &other );
        /** @return true iff this range is a subset of 'other'. */
        bool operator<=( const FieldRange &other ) const;

        /**
         * If there are any valid values for this range, the extreme values can
         * be extracted.
         */
        
        BSONElement min() const { assert( !empty() ); return _intervals[ 0 ]._lower._bound; }
        BSONElement max() const { assert( !empty() ); return _intervals[ _intervals.size() - 1 ]._upper._bound; }
        bool minInclusive() const { assert( !empty() ); return _intervals[ 0 ]._lower._inclusive; }
        bool maxInclusive() const { assert( !empty() ); return _intervals[ _intervals.size() - 1 ]._upper._inclusive; }

        /** @return true iff this range expresses a single equality interval. */
        bool equality() const;
        /** @return true if all the intervals for this range are equalities */
        bool inQuery() const;
        /** @return true iff this range does not include every BSONElement */
        bool nontrivial() const;
        /** @return true iff this range matches no BSONElements. */
        bool empty() const { return _intervals.empty(); }
        
        /** Empty the range so it matches no BSONElements. */
        void makeEmpty() { _intervals.clear(); }
        const vector<FieldInterval> &intervals() const { return _intervals; }
        string getSpecial() const { return _special; }
        /** Make component intervals noninclusive. */
        void setExclusiveBounds();
        /**
         * Constructs a range where all FieldIntervals and FieldBounds are in
         * the opposite order of the current range.
         * NOTE the resulting intervals might not be strictValid().
         */
        void reverse( FieldRange &ret ) const;
    private:
        BSONObj addObj( const BSONObj &o );
        void finishOperation( const vector<FieldInterval> &newIntervals, const FieldRange &other );
        vector<FieldInterval> _intervals;
        // Owns memory for our BSONElements.
        vector<BSONObj> _objData;
        string _special;
        bool _singleKey;
    };

    /**
     * A BoundList contains intervals specified by inclusive start
     * and end bounds.  The intervals should be nonoverlapping and occur in
     * the specified direction of traversal.  For example, given a simple index {i:1}
     * and direction +1, one valid BoundList is: (1, 2); (4, 6).  The same BoundList
     * would be valid for index {i:-1} with direction -1.
     */
    typedef vector<pair<BSONObj,BSONObj> > BoundList;

    class QueryPattern;
    
    /**
     * A set of FieldRanges determined from constraints on the fields of a query,
     * that may be used to determine index bounds.
     */
    class FieldRangeSet {
    public:
        friend class OrRangeGenerator;
        friend class FieldRangeVector;
        FieldRangeSet( const char *ns, const BSONObj &query , bool singleKey , bool optimize=true );
        
        /** @return true if there is a nontrivial range for the given field. */
        bool hasRange( const char *fieldName ) const {
            map<string, FieldRange>::const_iterator f = _ranges.find( fieldName );
            return f != _ranges.end();
        }
        /** @return range for the given field. */
        const FieldRange &range( const char *fieldName ) const;
        /** @return range for the given field. */
        FieldRange &range( const char *fieldName );
        /** @return the number of nontrivial ranges. */
        int nNontrivialRanges() const;
        /** 
         * @return true if a match could be possible on every field. Generally this
         * is not useful information for a single key FieldRangeSet and
         * matchPossibleForIndex() should be used instead.
         */
        bool matchPossible() const;
        /**
         * @return true if a match could be possible given the value of _singleKey
         * and index key 'keyPattern'.
         * @param keyPattern May be {} or {$natural:1} for a non index scan.
         */
        bool matchPossibleForIndex( const BSONObj &keyPattern ) const;
        
        const char *ns() const { return _ns; }
        
        /**
         * @return a simplified query from the extreme values of the nontrivial
         * fields.
         * @param fields If specified, the fields of the returned object are
         * ordered to match those of 'fields'.
         */
        BSONObj simplifiedQuery( const BSONObj &fields = BSONObj() ) const;
        
        QueryPattern pattern( const BSONObj &sort = BSONObj() ) const;
        string getSpecial() const;

        /**
         * @return a FieldRangeSet approximation of the documents in 'this' but
         * not in 'other'.  The approximation will be a superset of the documents
         * in 'this' but not 'other'.
         */
        const FieldRangeSet &operator-=( const FieldRangeSet &other );
        /** @return intersection of 'this' with 'other'. */
        const FieldRangeSet &operator&=( const FieldRangeSet &other );
        
        /**
         * @return an ordered list of bounds generated using an index key pattern
         * and traversal direction.
         *
         * NOTE This function is deprecated in the query optimizer and only
         * currently used by the sharding code.
         */
        BoundList indexBounds( const BSONObj &keyPattern, int direction ) const;

        /**
         * @return - A new FieldRangeSet based on this FieldRangeSet, but with only
         * a subset of the fields.
         * @param fields - Only fields which are represented as field names in this object
         * will be included in the returned FieldRangeSet.
         */
        FieldRangeSet *subset( const BSONObj &fields ) const;
        
        bool singleKey() const { return _singleKey; }
        
        BSONObj originalQuery() const { return _queries[ 0 ]; }
    private:
        void appendQueries( const FieldRangeSet &other );
        void makeEmpty();
        void processQueryField( const BSONElement &e, bool optimize );
        void processOpElement( const char *fieldName, const BSONElement &f, bool isNot, bool optimize );
        static FieldRange *__singleKeyTrivialRange;
        static FieldRange *__multiKeyTrivialRange;
        const FieldRange &trivialRange() const;
        map<string,FieldRange> _ranges;
        const char *_ns;
        // Owns memory for FieldRange BSONElements.
        vector<BSONObj> _queries;
        bool _singleKey;
    };

    class NamespaceDetails;
    
    /**
     * A pair of FieldRangeSets, one representing constraints for single key
     * indexes and the other representing constraints for multi key indexes and
     * unindexed scans.  In several member functions the caller is asked to
     * supply an index so that the implementation may utilize the proper
     * FieldRangeSet and return results that are appropriate with respect to that
     * supplied index.
     */
    class FieldRangeSetPair {
    public:
        FieldRangeSetPair( const char *ns, const BSONObj &query, bool optimize=true )
        :_singleKey( ns, query, true, optimize ), _multiKey( ns, query, false, optimize ) {}

        /**
         * @return the appropriate single or multi key FieldRangeSet for the specified index.
         * @param idxNo -1 for non index scan.
         */
        const FieldRangeSet &frsForIndex( const NamespaceDetails* nsd, int idxNo ) const;

        /** @return a field range in the single key FieldRangeSet. */
        const FieldRange &singleKeyRange( const char *fieldName ) const {
            return _singleKey.range( fieldName );
        }
        /** @return true if the range limits are equivalent to an empty query. */
        bool noNontrivialRanges() const;
        /** @return false if a match is impossible regardless of index. */
        bool matchPossible() const { return _multiKey.matchPossible(); }
        /**
         * @return false if a match is impossible on the specified index.
         * @param idxNo -1 for non index scan.
         */
        bool matchPossibleForIndex( NamespaceDetails *d, int idxNo, const BSONObj &keyPattern ) const;
        
        const char *ns() const { return _singleKey.ns(); }

        string getSpecial() const { return _singleKey.getSpecial(); }

        /** Intersect with another FieldRangeSetPair. */
        FieldRangeSetPair &operator&=( const FieldRangeSetPair &other );
        /**
         * Subtract a FieldRangeSet, generally one expressing a range that has
         * already been scanned.
         */
        FieldRangeSetPair &operator-=( const FieldRangeSet &scanned );

        BoundList singleKeyIndexBounds( const BSONObj &keyPattern, int direction ) const {
            return _singleKey.indexBounds( keyPattern, direction );
        }
        
        BSONObj originalQuery() const { return _singleKey.originalQuery(); }

    private:
        FieldRangeSetPair( const FieldRangeSet &singleKey, const FieldRangeSet &multiKey )
        :_singleKey( singleKey ), _multiKey( multiKey ) {}
        void assertValidIndex( const NamespaceDetails *d, int idxNo ) const;
        void assertValidIndexOrNoIndex( const NamespaceDetails *d, int idxNo ) const;
        /** matchPossibleForIndex() must be true. */
        BSONObj simplifiedQueryForIndex( NamespaceDetails *d, int idxNo, const BSONObj &keyPattern ) const;        
        FieldRangeSet _singleKey;
        FieldRangeSet _multiKey;
        friend class OrRangeGenerator;
        friend struct QueryUtilIndexed;
    };
    
    class IndexSpec;

    /**
     * An ordered list of fields and their FieldRanges, correspoinding to valid
     * index keys for a given index spec.
     */
    class FieldRangeVector {
    public:
        /**
         * @param frs The valid ranges for all fields, as defined by the query spec
         * @param indexSpec The index spec (key pattern and info)
         * @param direction The direction of index traversal
         */
        FieldRangeVector( const FieldRangeSet &frs, const IndexSpec &indexSpec, int direction );

        /** @return the number of index ranges represented by 'this' */
        long long size();
        /** @return starting point for an index traversal. */
        BSONObj startKey() const;
        /** @return end point for an index traversal. */
        BSONObj endKey() const;
        /** @return a client readable representation of 'this' */
        BSONObj obj() const;
        
        /**
         * @return true iff the provided document matches valid ranges on all
         * of this FieldRangeVector's fields, which is the case iff this document
         * would be returned while scanning the index corresponding to this
         * FieldRangeVector.  This function is used for $or clause deduping.
         */
        bool matches( const BSONObj &obj ) const;
        
    private:
        int matchingLowElement( const BSONElement &e, int i, bool direction, bool &lowEquality ) const;
        bool matchesElement( const BSONElement &e, int i, bool direction ) const;
        vector<FieldRange> _ranges;
        const IndexSpec &_indexSpec;
        int _direction;
        vector<BSONObj> _queries; // make sure mem owned
        friend class FieldRangeVectorIterator;
    };
    
    /**
     * Helper class for iterating through an ordered representation of keys
     * to find those keys that match a specified FieldRangeVector.
     */
    class FieldRangeVectorIterator {
    public:
        FieldRangeVectorIterator( const FieldRangeVector &v ) : _v( v ), _i( _v._ranges.size(), -1 ), _cmp( _v._ranges.size(), 0 ), _inc( _v._ranges.size(), false ), _after() {
        }
        static BSONObj minObject() {
            BSONObjBuilder b; b.appendMinKey( "" );
            return b.obj();
        }
        static BSONObj maxObject() {
            BSONObjBuilder b; b.appendMaxKey( "" );
            return b.obj();
        }
        /**
         * @return Suggested advance method, based on current key.
         *   -2 Iteration is complete, no need to advance.
         *   -1 Advance to the next key, without skipping.
         *  >=0 Skip parameter.  If @return is r, skip to the key comprised
         *      of the first r elements of curr followed by the (r+1)th and
         *      remaining elements of cmp() (with inclusivity specified by
         *      the (r+1)th and remaining elements of inc()).  If after() is
         *      true, skip past this key not to it.
         */
        int advance( const BSONObj &curr );
        const vector<const BSONElement *> &cmp() const { return _cmp; }
        const vector<bool> &inc() const { return _inc; }
        bool after() const { return _after; }
        void prepDive();
        void setZero( int i ) { for( int j = i; j < (int)_i.size(); ++j ) _i[ j ] = 0; }
        void setMinus( int i ) { for( int j = i; j < (int)_i.size(); ++j ) _i[ j ] = -1; }
        bool ok() { return _i[ 0 ] < (int)_v._ranges[ 0 ].intervals().size(); }
        BSONObj startKey();
        // temp
        BSONObj endKey();
    private:
        const FieldRangeVector &_v;
        vector<int> _i;
        vector<const BSONElement*> _cmp;
        vector<bool> _inc;
        bool _after;
    };
    
    /**
     * As we iterate through $or clauses this class generates a FieldRangeSetPair
     * for the current $or clause, in some cases by excluding ranges that were
     * included in a previous clause.
     */
    class OrRangeGenerator {
    public:
        OrRangeGenerator( const char *ns, const BSONObj &query , bool optimize=true );

        /**
         * @return true iff we are done scanning $or clauses.  if there's a
         * useless or clause, we won't use or index ranges to help with scanning.
         */
        bool orFinished() const { return _orFound && _orSets.empty(); }
        /** Iterates to the next $or clause by removing the current $or clause. */
        void popOrClause( NamespaceDetails *nsd, int idxNo, const BSONObj &keyPattern );
        void popOrClauseSingleKey();
        /** @return FieldRangeSetPair for the current $or clause. */
        FieldRangeSetPair *topFrsp() const;
        /**
         * @return original FieldRangeSetPair for the current $or clause. While the
         * original bounds are looser, they are composed of fewer ranges and it
         * is faster to do operations with them; when they can be used instead of
         * more precise bounds, they should.
         */
        FieldRangeSetPair *topFrspOriginal() const;
        
        string getSpecial() const { return _baseSet.getSpecial(); }

        bool moreOrClauses() const { return !_orSets.empty(); }
    private:
        void assertMayPopOrClause();
        void popOrClause( const FieldRangeSet *toDiff, NamespaceDetails *d = 0, int idxNo = -1, const BSONObj &keyPattern = BSONObj() );
        FieldRangeSetPair _baseSet;
        list<FieldRangeSetPair> _orSets;
        list<FieldRangeSetPair> _originalOrSets;
        // ensure memory is owned
        list<FieldRangeSetPair> _oldOrSets;
        bool _orFound;
        friend struct QueryUtilIndexed;
    };

    /** returns a string that when used as a matcher, would match a super set of regex()
        returns "" for complex regular expressions
        used to optimize queries in some simple regex cases that start with '^'

        if purePrefix != NULL, sets it to whether the regex can be converted to a range query
    */
    string simpleRegex(const char* regex, const char* flags, bool* purePrefix=NULL);

    /** returns the upper bound of a query that matches prefix */
    string simpleRegexEnd( string prefix );

    long long applySkipLimit( long long num , const BSONObj& cmd );

} // namespace mongo

#include "queryutil-inl.h"