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
|
// @file queryoptimizercursorimpl.h - A cursor interleaving multiple candidate cursors.
/**
* Copyright (C) 2011 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 "queryoptimizer.h"
#include "queryoptimizercursor.h"
namespace mongo {
/** Helper class for caching and counting matches during execution of a QueryPlan. */
class CachedMatchCounter {
public:
/**
* @param aggregateNscanned - shared count of nscanned for this and othe plans.
* @param cumulativeCount - starting point for accumulated count over a series of plans.
*/
CachedMatchCounter( long long &aggregateNscanned, int cumulativeCount ) : _aggregateNscanned( aggregateNscanned ), _nscanned(), _cumulativeCount( cumulativeCount ), _count(), _checkDups(), _match( Unknown ), _counted() {}
/** Set whether dup checking is enabled when counting. */
void setCheckDups( bool checkDups ) { _checkDups = checkDups; }
/**
* Usual sequence of events:
* 1) resetMatch() - reset stored match value to Unkonwn.
* 2) setMatch() - set match value to a definite true/false value.
* 3) knowMatch() - check if setMatch() has been called.
* 4) countMatch() - increment count if match is true.
*/
void resetMatch() {
_match = Unknown;
_counted = false;
}
/** @return true if the match was not previously recorded. */
bool setMatch( bool match ) {
MatchState oldMatch = _match;
_match = match ? True : False;
return _match == True && oldMatch != True;
}
bool knowMatch() const { return _match != Unknown; }
void countMatch( const DiskLoc &loc ) {
if ( !_counted && _match == True && !getsetdup( loc ) ) {
++_cumulativeCount;
++_count;
_counted = true;
}
}
bool wouldCountMatch( const DiskLoc &loc ) const {
return !_counted && _match == True && !getdup( loc );
}
bool enoughCumulativeMatchesToChooseAPlan() const {
// This is equivalent to the default condition for switching from
// a query to a getMore, which was the historical default match count for
// choosing a plan.
return _cumulativeCount >= 101;
}
bool enoughMatchesToRecordPlan() const {
// Recording after 50 matches is a historical default (101 default limit / 2).
return _count > 50;
}
int cumulativeCount() const { return _cumulativeCount; }
int count() const { return _count; }
/** Update local and aggregate nscanned counts. */
void updateNscanned( long long nscanned ) {
_aggregateNscanned += ( nscanned - _nscanned );
_nscanned = nscanned;
}
long long nscanned() const { return _nscanned; }
long long &aggregateNscanned() const { return _aggregateNscanned; }
private:
bool getsetdup( const DiskLoc &loc ) {
if ( !_checkDups ) {
return false;
}
pair<set<DiskLoc>::iterator, bool> p = _dups.insert( loc );
return !p.second;
}
bool getdup( const DiskLoc &loc ) const {
if ( !_checkDups ) {
return false;
}
return _dups.find( loc ) != _dups.end();
}
long long &_aggregateNscanned;
long long _nscanned;
int _cumulativeCount;
int _count;
bool _checkDups;
enum MatchState { Unknown, False, True };
MatchState _match;
bool _counted;
set<DiskLoc> _dups;
};
/** Dup tracking class, optimizing one common case with small set and few initial reads. */
class SmallDupSet {
public:
SmallDupSet() : _accesses() {
_vec.reserve( 250 );
}
/** @return true if @param 'loc' already added to the set, false if adding to the set in this call. */
bool getsetdup( const DiskLoc &loc ) {
access();
return vec() ? getsetdupVec( loc ) : getsetdupSet( loc );
}
/** @return true when @param loc in the set. */
bool getdup( const DiskLoc &loc ) {
access();
return vec() ? getdupVec( loc ) : getdupSet( loc );
}
private:
void access() {
++_accesses;
mayUpgrade();
}
void mayUpgrade() {
if ( vec() && _accesses > 500 ) {
_set.insert( _vec.begin(), _vec.end() );
}
}
bool vec() const {
return _set.size() == 0;
}
bool getsetdupVec( const DiskLoc &loc ) {
if ( getdupVec( loc ) ) {
return true;
}
_vec.push_back( loc );
return false;
}
bool getdupVec( const DiskLoc &loc ) const {
for( vector<DiskLoc>::const_iterator i = _vec.begin(); i != _vec.end(); ++i ) {
if ( *i == loc ) {
return true;
}
}
return false;
}
bool getsetdupSet( const DiskLoc &loc ) {
pair<set<DiskLoc>::iterator, bool> p = _set.insert(loc);
return !p.second;
}
bool getdupSet( const DiskLoc &loc ) {
return _set.count( loc ) > 0;
}
vector<DiskLoc> _vec;
set<DiskLoc> _set;
long long _accesses;
};
/**
* Helper class for generating a simple Cursor or QueryOptimizerCursor from a set of query
* parameters. This class was refactored from a single function call and is not expected to
* outlive its constructor arguments.
*/
class CursorGenerator {
public:
CursorGenerator( const char *ns,
const BSONObj &query,
const BSONObj &order,
const QueryPlanSelectionPolicy &planPolicy,
bool *simpleEqualityMatch,
const ParsedQuery *parsedQuery,
QueryPlan::Summary *singlePlanSummary );
shared_ptr<Cursor> generate();
private:
bool snapshot() const { return _parsedQuery && _parsedQuery->isSnapshot(); }
bool explain() const { return _parsedQuery && _parsedQuery->isExplain(); }
BSONObj min() const { return _parsedQuery ? _parsedQuery->getMin() : BSONObj(); }
BSONObj max() const { return _parsedQuery ? _parsedQuery->getMax() : BSONObj(); }
shared_ptr<Projection> fieldsPtr() const {
return _parsedQuery ? _parsedQuery->getFieldPtr() : shared_ptr<Projection>();
}
int numWanted() const {
return _parsedQuery ? ( _parsedQuery->getSkip() + _parsedQuery->getNumToReturn() ) : 0;
}
/** If no ParsedQuery was supplied, it's assumed no reordering will be applied. */
bool requireOrder() const { return _parsedQuery == 0; }
bool mayShortcutQueryOptimizer() const {
return min().isEmpty() && max().isEmpty() && !fieldsPtr() && _argumentsHint.isEmpty();
}
BSONObj hint() const {
return _argumentsHint.isEmpty() ? _planPolicy.planHint( _ns ) : _argumentsHint;
}
void setArgumentsHint();
shared_ptr<Cursor> shortcutCursor() const;
void setMultiPlanScanner();
shared_ptr<Cursor> singlePlanCursor();
const char *_ns;
BSONObj _query;
BSONObj _order;
const QueryPlanSelectionPolicy &_planPolicy;
bool *_simpleEqualityMatch;
const ParsedQuery *_parsedQuery;
QueryPlan::Summary *_singlePlanSummary;
BSONObj _argumentsHint;
auto_ptr<MultiPlanScanner> _mps;
};
} // namespace mongo
|
