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
|
/**
* Copyright (C) 2014 MongoDB 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.
*/
#include "mongo/platform/basic.h"
#include "mongo/client/dbclientinterface.h"
#include "mongo/db/commands.h"
#include "mongo/db/query/explain.h"
#include "mongo/s/query/cluster_find.h"
namespace mongo {
namespace {
/**
* Implements the explain command on mongos.
*
* "Old-style" explains (i.e. queries which have the $explain flag set), do not run
* through this path. Such explains will be supported for backwards compatibility,
* and must succeed in multiversion clusters.
*
* "New-style" explains use the explain command. When the explain command is routed
* through mongos, it is forwarded to all relevant shards. If *any* shard does not
* support a new-style explain, then the entire explain will fail (i.e. new-style
* explains cannot be used in multiversion clusters).
*/
class ClusterExplainCmd : public BasicCommand {
MONGO_DISALLOW_COPYING(ClusterExplainCmd);
public:
ClusterExplainCmd() : BasicCommand("explain") {}
virtual bool supportsWriteConcern(const BSONObj& cmd) const override {
return false;
}
/**
* Running an explain on a secondary requires explicitly setting slaveOk.
*/
virtual bool slaveOk() const {
return false;
}
virtual bool slaveOverrideOk() const {
return true;
}
virtual bool maintenanceOk() const {
return false;
}
virtual bool adminOnly() const {
return false;
}
virtual void help(std::stringstream& help) const {
help << "explain database reads and writes";
}
/**
* You are authorized to run an explain if you are authorized to run
* the command that you are explaining. The auth check is performed recursively
* on the nested command.
*/
virtual Status checkAuthForOperation(OperationContext* opCtx,
const std::string& dbname,
const BSONObj& cmdObj) {
if (Object != cmdObj.firstElement().type()) {
return Status(ErrorCodes::BadValue, "explain command requires a nested object");
}
BSONObj explainObj = cmdObj.firstElement().Obj();
Command* commToExplain = Command::findCommand(explainObj.firstElementFieldName());
if (NULL == commToExplain) {
mongoutils::str::stream ss;
ss << "unknown command: " << explainObj.firstElementFieldName();
return Status(ErrorCodes::CommandNotFound, ss);
}
return commToExplain->checkAuthForOperation(opCtx, dbname, explainObj);
}
virtual bool run(OperationContext* opCtx,
const std::string& dbName,
const BSONObj& cmdObj,
std::string& errmsg,
BSONObjBuilder& result) {
auto verbosity = ExplainOptions::parseCmdBSON(cmdObj);
if (!verbosity.isOK()) {
return appendCommandStatus(result, verbosity.getStatus());
}
// This is the nested command which we are explaining. We need to propagate generic
// arguments into the inner command since it is what is passed to the virtual
// Command::explain() method.
const BSONObj explainObj = ([&] {
const auto innerObj = cmdObj.firstElement().Obj();
if (auto innerDb = innerObj["$db"]) {
uassert(ErrorCodes::InvalidNamespace,
str::stream() << "Mismatched $db in explain command. Expected " << dbName
<< " but got "
<< innerDb.checkAndGetStringData(),
innerDb.checkAndGetStringData() == dbName);
}
BSONObjBuilder bob;
bob.appendElements(innerObj);
for (auto outerElem : cmdObj) {
// If the argument is in both the inner and outer command, we currently let the
// inner version take precedence.
const auto name = outerElem.fieldNameStringData();
if (Command::isGenericArgument(name) && !innerObj.hasField(name)) {
bob.append(outerElem);
}
}
return bob.obj();
}());
const std::string cmdName = explainObj.firstElementFieldName();
Command* commToExplain = Command::findCommand(cmdName);
if (!commToExplain) {
return appendCommandStatus(
result,
Status{ErrorCodes::CommandNotFound,
str::stream() << "Explain failed due to unknown command: " << cmdName});
}
// Actually call the nested command's explain(...) method.
Status explainStatus =
commToExplain->explain(opCtx, dbName, explainObj, verbosity.getValue(), &result);
if (!explainStatus.isOK()) {
return appendCommandStatus(result, explainStatus);
}
return true;
}
} cmdExplainCluster;
} // namespace
} // namespace mongo
|
