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
|
/**
* Copyright (C) 2008 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/>.
*/
#pragma once
#include "../pch.h"
#include "jsobj.h"
#include "diskloc.h"
#include "matcher.h"
namespace mongo {
class Record;
class CoveredIndexMatcher;
/* Query cursors, base class. This is for our internal cursors. "ClientCursor" is a separate
concept and is for the user's cursor.
WARNING concurrency: the vfunctions below are called back from within a
ClientCursor::ccmutex. Don't cause a deadlock, you've been warned.
*/
class Cursor : boost::noncopyable {
public:
virtual ~Cursor() {}
virtual bool ok() = 0;
bool eof() { return !ok(); }
virtual Record* _current() = 0;
virtual BSONObj current() = 0;
virtual DiskLoc currLoc() = 0;
virtual bool advance() = 0; /*true=ok*/
virtual BSONObj currKey() const { return BSONObj(); }
// DiskLoc the cursor requires for continued operation. Before this
// DiskLoc is deleted, the cursor must be incremented or destroyed.
virtual DiskLoc refLoc() = 0;
/* Implement these if you want the cursor to be "tailable" */
/* Request that the cursor starts tailing after advancing past last record. */
/* The implementation may or may not honor this request. */
virtual void setTailable() {}
/* indicates if tailing is enabled. */
virtual bool tailable() {
return false;
}
virtual void aboutToDeleteBucket(const DiskLoc& b) { }
/* optional to implement. if implemented, means 'this' is a prototype */
virtual Cursor* clone() {
return 0;
}
virtual BSONObj indexKeyPattern() {
return BSONObj();
}
/* called after every query block is iterated -- i.e. between getMore() blocks
so you can note where we are, if necessary.
*/
virtual void noteLocation() { }
/* called before query getmore block is iterated */
virtual void checkLocation() { }
virtual bool supportGetMore() = 0;
virtual bool supportYields() = 0;
virtual string toString() { return "abstract?"; }
/* used for multikey index traversal to avoid sending back dups. see Matcher::matches().
if a multikey index traversal:
if loc has already been sent, returns true.
otherwise, marks loc as sent.
@param deep - match was against an array, so we know it is multikey. this is legacy and kept
for backwards datafile compatibility. 'deep' can be eliminated next time we
force a data file conversion. 7Jul09
*/
virtual bool getsetdup(DiskLoc loc) = 0;
virtual BSONObj prettyIndexBounds() const { return BSONArray(); }
virtual bool capped() const { return false; }
// The implementation may return different matchers depending on the
// position of the cursor. If matcher() is nonzero at the start,
// matcher() should be checked each time advance() is called.
virtual CoveredIndexMatcher *matcher() const { return 0; }
// A convenience function for setting the value of matcher() manually
// so it may accessed later. Implementations which must generate
// their own matcher() should assert here.
virtual void setMatcher( shared_ptr< CoveredIndexMatcher > matcher ) {
massert( 13285, "manual matcher config not allowed", false );
}
};
// strategy object implementing direction of traversal.
class AdvanceStrategy {
public:
virtual ~AdvanceStrategy() { }
virtual DiskLoc next( const DiskLoc &prev ) const = 0;
};
const AdvanceStrategy *forward();
const AdvanceStrategy *reverse();
/* table-scan style cursor */
class BasicCursor : public Cursor {
protected:
DiskLoc curr, last;
const AdvanceStrategy *s;
private:
bool tailable_;
shared_ptr< CoveredIndexMatcher > _matcher;
void init() {
tailable_ = false;
}
public:
bool ok() {
return !curr.isNull();
}
Record* _current() {
assert( ok() );
return curr.rec();
}
BSONObj current() {
Record *r = _current();
BSONObj j(r);
return j;
}
virtual DiskLoc currLoc() {
return curr;
}
virtual DiskLoc refLoc() {
return curr.isNull() ? last : curr;
}
bool advance();
BasicCursor(DiskLoc dl, const AdvanceStrategy *_s = forward()) : curr(dl), s( _s ) {
init();
}
BasicCursor(const AdvanceStrategy *_s = forward()) : s( _s ) {
init();
}
virtual string toString() {
return "BasicCursor";
}
virtual void setTailable() {
if ( !curr.isNull() || !last.isNull() )
tailable_ = true;
}
virtual bool tailable() {
return tailable_;
}
virtual bool getsetdup(DiskLoc loc) { return false; }
virtual bool supportGetMore() { return true; }
virtual bool supportYields() { return true; }
virtual CoveredIndexMatcher *matcher() const { return _matcher.get(); }
virtual void setMatcher( shared_ptr< CoveredIndexMatcher > matcher ) {
_matcher = matcher;
}
};
/* used for order { $natural: -1 } */
class ReverseCursor : public BasicCursor {
public:
ReverseCursor(DiskLoc dl) : BasicCursor( dl, reverse() ) { }
ReverseCursor() : BasicCursor( reverse() ) { }
virtual string toString() {
return "ReverseCursor";
}
};
class NamespaceDetails;
class ForwardCappedCursor : public BasicCursor, public AdvanceStrategy {
public:
ForwardCappedCursor( NamespaceDetails *nsd = 0, const DiskLoc &startLoc = DiskLoc() );
virtual string toString() {
return "ForwardCappedCursor";
}
virtual DiskLoc next( const DiskLoc &prev ) const;
virtual bool capped() const { return true; }
private:
NamespaceDetails *nsd;
};
class ReverseCappedCursor : public BasicCursor, public AdvanceStrategy {
public:
ReverseCappedCursor( NamespaceDetails *nsd = 0, const DiskLoc &startLoc = DiskLoc() );
virtual string toString() {
return "ReverseCappedCursor";
}
virtual DiskLoc next( const DiskLoc &prev ) const;
virtual bool capped() const { return true; }
private:
NamespaceDetails *nsd;
};
} // namespace mongo
|
