TRACE
- 语法图
- 示例
  - Row
  - JSON
  - Log
- MySQL 兼容性
- 另请参阅

TRACE

TRACE 语句用于提供查询执行的详细信息，可通过 TiDB 服务器状态端口所公开的图形界面进行查看。

语法图

TraceStmt

TracableStmt

1. TraceStmt ::=
2. "TRACE" ( "FORMAT" "=" stringLit )? TracableStmt

4. TracableStmt ::=
5. ( SelectStmt | DeleteFromStmt | UpdateStmt | InsertIntoStmt | ReplaceIntoStmt | UnionStmt | LoadDataStmt | BeginTransactionStmt | CommitStmt | RollbackStmt | SetStmt )

Format	描述
`row`	以树形格式输出
`json`	以 JSON 格式结构化输出
`log`	基于日志输出

示例

Row

1. TRACE FORMAT='row' SELECT * FROM mysql.user;

1. +--------------------------------------------+-----------------+------------+
2. | operation                                  | startTS         | duration   |
3. +--------------------------------------------+-----------------+------------+
4. | trace                                      | 17:03:31.938237 | 886.086µs  |
5. |   ├─session.Execute                        | 17:03:31.938247 | 507.812µs  |
6. |   │ ├─session.ParseSQL                     | 17:03:31.938254 | 22.504µs   |
7. |   │ ├─executor.Compile                     | 17:03:31.938321 | 278.931µs  |
8. |   │ │ └─session.getTxnFuture               | 17:03:31.938337 | 1.515µs    |
9. |   │ └─session.runStmt                      | 17:03:31.938613 | 109.578µs  |
10. |   │   ├─TableReaderExecutor.Open           | 17:03:31.938645 | 50.657µs   |
11. |   │   │ └─distsql.Select                   | 17:03:31.938666 | 21.066µs   |
12. |   │   │   └─RPCClient.SendRequest          | 17:03:31.938799 | 158.411µs  |
13. |   │   └─session.CommitTxn                  | 17:03:31.938705 | 12.06µs    |
14. |   │     └─session.doCommitWitRetry         | 17:03:31.938709 | 2.437µs    |
15. |   ├─*executor.TableReaderExecutor.Next     | 17:03:31.938781 | 224.327µs  |
16. |   └─*executor.TableReaderExecutor.Next     | 17:03:31.939019 | 6.266µs    |
17. +--------------------------------------------+-----------------+------------+
18. 13 rows in set (0.00 sec)

JSON

1. TRACE FORMAT='json' SELECT * FROM mysql.user;

可将 JSON 格式的跟踪文件粘贴到跟踪查看器中。查看器可通过 TiDB 状态端口访问：

Log

1. TRACE FORMAT='log' SELECT * FROM mysql.user;

1. +----------------------------+--------------------------------------------------------+------+------------------------------------+
2. | time                       | event                                                  | tags | spanName                           |
3. +----------------------------+--------------------------------------------------------+------+------------------------------------+
4. | 2024-04-08 08:41:47.358734 | --- start span trace ----                              |      | trace                              |
5. | 2024-04-08 08:41:47.358737 | --- start span session.ExecuteStmt ----                |      | session.ExecuteStmt                |
6. | 2024-04-08 08:41:47.358746 | --- start span executor.Compile ----                   |      | executor.Compile                   |
7. | 2024-04-08 08:41:47.358984 | --- start span session.runStmt ----                    |      | session.runStmt                    |
8. | 2024-04-08 08:41:47.359035 | --- start span TableReaderExecutor.Open ----           |      | TableReaderExecutor.Open           |
9. | 2024-04-08 08:41:47.359047 | --- start span distsql.Select ----                     |      | distsql.Select                     |
10. | 2024-04-08 08:41:47.359073 | --- start span *executor.TableReaderExecutor.Next ---- |      | *executor.TableReaderExecutor.Next |
11. | 2024-04-08 08:41:47.359077 | table scan table: user, range: [[-inf,+inf]]           |      | *executor.TableReaderExecutor.Next |
12. | 2024-04-08 08:41:47.359094 | --- start span regionRequest.SendReqCtx ----           |      | regionRequest.SendReqCtx           |
13. | 2024-04-08 08:41:47.359098 | send Cop request to region 16 at store1                |      | regionRequest.SendReqCtx           |
14. | 2024-04-08 08:41:47.359237 | --- start span *executor.TableReaderExecutor.Next ---- |      | *executor.TableReaderExecutor.Next |
15. | 2024-04-08 08:41:47.359240 | table scan table: user, range: [[-inf,+inf]]           |      | *executor.TableReaderExecutor.Next |
16. | 2024-04-08 08:41:47.359242 | execute done, ReturnRow: 1, ModifyRow: 0               |      | trace                              |
17. | 2024-04-08 08:41:47.359252 | execute done, modify row: 0                            |      | trace                              |
18. +----------------------------+--------------------------------------------------------+------+------------------------------------+
19. 14 rows in set (0.0008 sec)

MySQL 兼容性

TRACE 语句是 TiDB 对 MySQL 语法的扩展。

另请参阅

EXPLAIN ANALYZE