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
|
/**
* Copyright (C) 2013 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.
*/
#pragma once
#include <string>
#include "mongo/db/query/explain_common.h"
#include "mongo/s/commands/strategy.h"
#include "mongo/s/write_ops/batched_command_request.h"
namespace mongo {
class OperationContext;
namespace rpc {
class ServerSelectionMetadata;
} // namespace rpc
/**
* Namespace for the collection of static methods used by commands in the implementation of
* explain on mongos.
*/
class ClusterExplain {
public:
/**
* Given the BSON specification for a command, 'cmdObj', wraps the object in order to produce
* the BSON for an explain of that command, at the given verbosity level 'verbosity.'
*
* Adds the result to the BSONObjBuidler 'out'.
*
* Unlike wrapAsExplain, does not downconvert the command to OP_QUERY. Should be used for paths
* that send the command over the NetworkInterfaceASIO rather than DBClient.
*/
static void wrapAsExplainForOP_COMMAND(const BSONObj& cmdObj,
ExplainCommon::Verbosity verbosity,
BSONObjBuilder* explainBuilder);
/**
* Given the BSON specification for a command, 'cmdObj', wraps the object in order to
* produce the BSON for an explain of that command, at the given verbosity level
* 'verbosity' and according to the metadata in 'serverSelectionMetadata'.
*
* Adds the result to the BSONObj builder 'out'.
*
* Also uses 'serverSelectionMetdata' to set 'optionsOut' to the options bit vector that should
* be forwarded to the shards.
*/
static void wrapAsExplain(const BSONObj& cmdObj,
ExplainCommon::Verbosity verbosity,
const rpc::ServerSelectionMetadata& serverSelectionMetadata,
BSONObjBuilder* out,
int* optionsOut);
/**
* Determines the kind of "execution stage" that mongos would use in order to collect
* the results from the shards, assuming that the command being explained is a read
* operation such as find or count.
*/
static const char* getStageNameForReadOp(
const std::vector<Strategy::CommandResult>& shardResults, const BSONObj& explainObj);
/**
* Command implementations on mongos use this method to construct the sharded explain
* output format based on the results from the shards in 'shardResults'.
*
* On success, the output is added to the BSONObj builder 'out'.
*/
static Status buildExplainResult(OperationContext* txn,
const std::vector<Strategy::CommandResult>& shardResults,
const char* mongosStageName,
long long millisElapsed,
BSONObjBuilder* out);
//
// Names of mock mongos execution stages.
//
static const char* kSingleShard;
static const char* kMergeFromShards;
static const char* kMergeSortFromShards;
static const char* kWriteOnShards;
private:
/**
* Returns an OK status if all shards support the explain command and returned sensible
* results. Otherwise, returns a non-OK status and the entire explain should fail.
*/
static Status validateShardResults(const std::vector<Strategy::CommandResult>& shardResults);
/**
* Populates the BSONObj builder 'out' with query planner explain information, based on
* the results from the shards contained in 'shardResults'.
*
* The planner info will display 'mongosStageName' as the name of the execution stage
* performed by mongos after gathering results from the shards.
*/
static void buildPlannerInfo(OperationContext* txn,
const std::vector<Strategy::CommandResult>& shardResults,
const char* mongosStageName,
BSONObjBuilder* out);
/**
* Populates the BSONObj builder 'out' with execution stats explain information,
* if the results from the shards in 'shardsResults' contain this info.
*
* Will display 'mongosStageName' as the name of the execution stage performed by mongos,
* and 'millisElapsed' as the execution time of the mongos stage.
*/
static void buildExecStats(const std::vector<Strategy::CommandResult>& shardResults,
const char* mongosStageName,
long long millisElapsed,
BSONObjBuilder* out);
};
} // namespace mongo
|
