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
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
|
/**
* Copyright (C) 2013 10gen Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License, version 3,
* as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the GNU Affero General Public License in all respects for
* all of the code used other than as permitted herein. If you modify file(s)
* with this exception, you may extend this exception to your version of the
* file(s), but you are not obligated to do so. If you do not wish to do so,
* delete this exception statement from your version. If you delete this
* exception statement from all source files in the program, then also delete
* it in the license file.
*/
#pragma once
#include <vector>
#include <set>
#include "mongo/db/jsobj.h"
namespace mongo {
/**
* Internal class used by BtreeAccessMethod to generate keys for indexed documents.
* This class is meant to be kept under the index access layer.
*/
class BtreeKeyGenerator {
public:
BtreeKeyGenerator(vector<const char*> fieldNames, vector<BSONElement> fixed, bool isSparse);
virtual ~BtreeKeyGenerator() { }
Status getKeys(const BSONObj &obj, BSONObjSet *keys) const;
protected:
// These are used by the getKeysImpl(s) below.
vector<const char*> _fieldNames;
bool _isSparse;
BSONObj _nullKey; // a full key with all fields null
BSONObj _nullObj; // only used for _nullElt
BSONElement _nullElt; // jstNull
BSONSizeTracker _sizeTracker;
private:
// We have V0 and V1. Sigh.
virtual Status getKeysImpl(vector<const char*> fieldNames, vector<BSONElement> fixed,
const BSONObj &obj, BSONObjSet *keys) const = 0;
vector<BSONElement> _fixed;
};
class BtreeKeyGeneratorV0 : public BtreeKeyGenerator {
public:
BtreeKeyGeneratorV0(vector<const char*> fieldNames, vector<BSONElement> fixed,
bool isSparse);
virtual ~BtreeKeyGeneratorV0() { }
private:
virtual Status getKeysImpl(vector<const char*> fieldNames, vector<BSONElement> fixed,
const BSONObj &obj, BSONObjSet *keys) const;
};
class BtreeKeyGeneratorV1 : public BtreeKeyGenerator {
public:
BtreeKeyGeneratorV1(vector<const char*> fieldNames, vector<BSONElement> fixed,
bool isSparse);
virtual ~BtreeKeyGeneratorV1() { }
private:
// Our approach to generating keys is to generate key parts for one field in
// the key pattern at a time. A 'KeyElementList' stores the elements extracted
// from the original BSON object for each index field individually. There is one
// outer list per key pattern field; the inner lists store the extracted elements
// that will be used to construct the keys.
//
// Ex.
// Say we have index {a: 1, b: 1} and we are generating keys for the object
// {a: 3, b: [4, 5, 6]}. The first step is to construct the following KeyElementList:
// [ [ El(3) ], [ El(4), El(5), El(6) ] ]
// where the notation El(n) denotes a BSONElement for a numeric field.
typedef vector< vector<BSONElement> > KeyElementList;
// Btree key generation is a recursive process. As we recur through the input BSONObj,
// we pass along a 'KeygenContext', which wraps up any state we need about where we
// are in the keygen process.
struct KeygenContext {
// Index into '_keyPattern' corresponding to the field that we are currently
// generating fields for. Ex: For key pattern {a: 1, b: 1, c: 1}, 'kpIndex'
// will be set to 0 when generating keys for "a", 1 when generating keys for "b",
// and 2 when generating keys for "c".
size_t kpIndex;
// Index which keeps track of where we are in the path of the indexed field.
// Ex: Say we have key pattern {a: 1, "b.c.d": 1, e: 1}, and we are currently
// generating keys for "b.c.d" (i.e. kpIndex==1). Then 'pathPosition' will be 0
// when generating keys for "b", 1 when generating keys for "b.c", and 2 when
// generating keys for "b.c.d".
size_t pathPosition;
// Are we generating keys for an element of an indexed array?
bool inArray;
};
/**
* Top-level key generation implementation for V1 btree indices. Parameters:
* 'fieldNames' -- A list of the field names in the index key pattern. For index
* {"a.b.c": 1, "foo": -1, "bar.0.a": 1}, then this will be ["a.b.c", "foo", "bar.0.a"]
* 'fixed' -- Required by the method signature in the superclass, but not used.
* 'obj' -- The object for which we will generate index keys.
*
* Returns the set of index keys generated from 'obj' according to the key pattern
* in 'fieldNames' through the out-parameter 'keys'.
*/
virtual Status getKeysImpl(vector<const char*> fieldNames, vector<BSONElement> fixed,
const BSONObj &obj, BSONObjSet *keys) const;
/**
* Generates keys for the BSONElement 'el' according to the context in 'context' and
* the index key pattern stored in '_keyPattern'.
*/
Status getKeysForElement(const BSONElement& el,
KeygenContext context,
vector<BSONElement>* out) const;
/**
* getKeysForElement(...) delegates to this function if 'el' is an indexed array. Special
* key generation logic for arrays lives here.
*/
Status getKeysForArrayElement(const BSONElement& el,
KeygenContext context,
vector<BSONElement>* out) const;
/**
* A helper for getKeysForArrayElement(...) which handles key patterns that have a
* positional element, such as {"a.0": 1}.
*
* Returns true through the out-parameter 'isPositional' if keys have been successively
* generated for a positional pattern. Otherwise sets 'isPositional' to false (returning
* a status of OK) and does nothing.
*/
Status handlePositionalKeypattern(const BSONElement& el,
KeygenContext context,
bool* isPositional,
vector<BSONElement>* out) const;
/**
* getKeysForElement(...) delegates to this function if 'el' is neither an indexed
* array nor an indexed subobject.
*/
Status getKeysForSimpleElement(const BSONElement& el,
KeygenContext context,
vector<BSONElement>* out) const;
/**
* Outputs the final btree keys in 'keys', constructing them using the extracted
* BSONElements in 'kel'.
*
* Ex.
* Continuing the example from above, suppose that 'kel' is as show below:
* [ [ El(3) ], [ El(4), El(5), El(6) ] ]
* We would return the following three keys:
* {"": 3, "": 4}
* {"": 3, "": 5}
* {"": 3, "": 6}
*/
void buildKeyObjects(const KeyElementList& kel, BSONObjSet *keys) const;
//
// Helper functions.
//
/**
* Returns an error status if 'obj' has multiple arrays at position 'pathPosition' that
* are indexed. This is made illegal because it would require generating keys for the
* Cartesian product.
*
* Ex:
* Say we have key pattern {"a.b": 1, "a.c": 1} and 'obj' is {a: {b: [1], c: [2]}}.
* This method will return an error when 'pathPosition' is 1, as both "a.b" and "a.c"
* are arrays.
*/
Status checkForParallelArrays(const BSONObj& obj, size_t pathPosition) const;
/**
* Returns true if 'context' points to the last position in the path for the
* current field.
*
* Ex.
* Say the keypattern is {"a": 1, "b.c.d": 1, "e": 1} and 'context.kpIndex'
* is 1 (we are generating keys for "b.c.d"). This function will return true
* if and only if 'context.pathPosition' is 2.
*/
bool lastPathPosition(const KeygenContext& context) const;
//
// Member vars.
//
// A representation of the key pattern as a list of list of strings. There is one outer
// list per field in the index. Each of these fields is represented as a lit of the dotted
// path components.
//
// Ex.
// Say the index is {"a.b.c": 1, "foo": -1, "bar.0.a": 1}. Then '_keyPattern' is:
// [ [ "a", "b", "c" ],
// [ "foo" ],
// [ "bar", "0", "a" ] ]
typedef vector< vector<string> > KeyPattern;
KeyPattern _keyPattern;
// The BSONObj {"": undefined}.
BSONObj _undefinedObj;
// A BSONElement containing value 'undefined'.
BSONElement _undefinedElt;
};
} // namespace mongo
|
