summaryrefslogtreecommitdiff
path: root/src/mongo/db/projection.h
blob: c4844f7a146d484a4338d1112df182d49894bcf9 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
// projection.h

/*    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 "mongo/pch.h"
#include "jsobj.h"

namespace mongo {

    // fwd decls
    class Matcher;
    class MatchDetails;

    /**
     * given a document and a projection specification
     * can transform the document
     * currently supports specifying which fields and $slice
     */
    class Projection {
    public:

        class KeyOnly {
        public:

            KeyOnly() : _stringSize(0) {}

            BSONObj hydrate( const BSONObj& key ) const;

            void addNo() { _add( false , "" ); }
            void addYes( const string& name ) { _add( true , name ); }

        private:

            void _add( bool b , const string& name ) {
                _include.push_back( b );
                _names.push_back( name );
                _stringSize += name.size();
            }

            vector<bool> _include; // one entry per field in key.  true iff should be in output
            vector<string> _names; // name of field since key doesn't have names

            int _stringSize;
        };

        enum ArrayOpType {
            ARRAY_OP_NORMAL = 0,
            ARRAY_OP_ELEM_MATCH,
            ARRAY_OP_POSITIONAL
        };

        Projection() :
            _include(true) ,
            _special(false) ,
            _includeID(true) ,
            _skip(0) ,
            _limit(-1) ,
            _arrayOpType(ARRAY_OP_NORMAL),
            _hasNonSimple(false) {
        }

        /**
         * called once per lifetime
         * e.g. { "x" : 1 , "a.y" : 1 }
         */
        void init( const BSONObj& spec );

        /**
         * @return the spec init was called with
         */
        BSONObj getSpec() const { return _source; }

        /**
         * transforms in according to spec
         */
        BSONObj transform( const BSONObj& in, const MatchDetails* details = NULL ) const;


        /**
         * transforms in according to spec
         */
        void transform( const BSONObj& in , BSONObjBuilder& b, const MatchDetails* details = NULL ) const;


        /**
         * @return if the keyPattern has all the information needed to return then
         *         return a new KeyOnly otherwise null
         *         NOTE: a key may have modified the actual data
         *               which has to be handled above this (arrays, geo)
         */
        KeyOnly* checkKey( const BSONObj& keyPattern ) const;

        bool includeID() const { return _includeID; }

        /**
         *  get the type of array operator for the projection
         *  @return     ARRAY_OP_NORMAL if no array projection modifier,
         *              ARRAY_OP_ELEM_MATCH if one or more $elemMatch specifier,
         *              ARRAY_OP_POSITIONAL if one '.$' projection specified
         */
        ArrayOpType getArrayOpType() const;

        /**
         * Validate the given query satisfies this projection's positional operator.
         * NOTE: this function is only used to validate projections with a positional operator.
         * @param   query       User-supplied query specifier
         * @return  Field name if found, empty string otherwise.
         */
        void validateQuery( const BSONObj query ) const;

    private:

        /**
         * appends e to b if user wants it
         * will descend into e if needed
         */
        void append( BSONObjBuilder& b , const BSONElement& e, const MatchDetails* details = NULL,
                     const ArrayOpType arrayOpType = ARRAY_OP_NORMAL ) const;

        void add( const string& field, bool include );
        void add( const string& field, int skip, int limit );
        void appendArray( BSONObjBuilder& b , const BSONObj& a , bool nested=false) const;

        bool _include; // true if default at this level is to include
        bool _special; // true if this level can't be skipped or included without recursing

        //TODO: benchmark vector<pair> vs map
        typedef map<string, boost::shared_ptr<Projection> > FieldMap;
        FieldMap _fields;
        BSONObj _source;
        bool _includeID;

        // used for $slice operator
        int _skip;
        int _limit;

        // used for $elemMatch and positional operator ($)
        typedef map<string, shared_ptr<Matcher> > Matchers;
        Matchers _matchers;
        ArrayOpType _arrayOpType;

        bool _hasNonSimple;
    };


}