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
TraceStmt ::=
"TRACE" ( "FORMAT" "=" stringLit )? TracableStmt
TracableStmt ::=
( 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
TRACE FORMAT='row' SELECT * FROM mysql.user;
+--------------------------------------------+-----------------+------------+
| operation | startTS | duration |
+--------------------------------------------+-----------------+------------+
| trace | 17:03:31.938237 | 886.086µs |
| ├─session.Execute | 17:03:31.938247 | 507.812µs |
| │ ├─session.ParseSQL | 17:03:31.938254 | 22.504µs |
| │ ├─executor.Compile | 17:03:31.938321 | 278.931µs |
| │ │ └─session.getTxnFuture | 17:03:31.938337 | 1.515µs |
| │ └─session.runStmt | 17:03:31.938613 | 109.578µs |
| │ ├─TableReaderExecutor.Open | 17:03:31.938645 | 50.657µs |
| │ │ └─distsql.Select | 17:03:31.938666 | 21.066µs |
| │ │ └─RPCClient.SendRequest | 17:03:31.938799 | 158.411µs |
| │ └─session.CommitTxn | 17:03:31.938705 | 12.06µs |
| │ └─session.doCommitWitRetry | 17:03:31.938709 | 2.437µs |
| ├─*executor.TableReaderExecutor.Next | 17:03:31.938781 | 224.327µs |
| └─*executor.TableReaderExecutor.Next | 17:03:31.939019 | 6.266µs |
+--------------------------------------------+-----------------+------------+
13 rows in set (0.00 sec)
JSON
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
TRACE FORMAT='log' SELECT * FROM mysql.user;
+----------------------------+--------------------------------------------------------+------+------------------------------------+
| time | event | tags | spanName |
+----------------------------+--------------------------------------------------------+------+------------------------------------+
| 2024-04-08 08:41:47.358734 | --- start span trace ---- | | trace |
| 2024-04-08 08:41:47.358737 | --- start span session.ExecuteStmt ---- | | session.ExecuteStmt |
| 2024-04-08 08:41:47.358746 | --- start span executor.Compile ---- | | executor.Compile |
| 2024-04-08 08:41:47.358984 | --- start span session.runStmt ---- | | session.runStmt |
| 2024-04-08 08:41:47.359035 | --- start span TableReaderExecutor.Open ---- | | TableReaderExecutor.Open |
| 2024-04-08 08:41:47.359047 | --- start span distsql.Select ---- | | distsql.Select |
| 2024-04-08 08:41:47.359073 | --- start span *executor.TableReaderExecutor.Next ---- | | *executor.TableReaderExecutor.Next |
| 2024-04-08 08:41:47.359077 | table scan table: user, range: [[-inf,+inf]] | | *executor.TableReaderExecutor.Next |
| 2024-04-08 08:41:47.359094 | --- start span regionRequest.SendReqCtx ---- | | regionRequest.SendReqCtx |
| 2024-04-08 08:41:47.359098 | send Cop request to region 16 at store1 | | regionRequest.SendReqCtx |
| 2024-04-08 08:41:47.359237 | --- start span *executor.TableReaderExecutor.Next ---- | | *executor.TableReaderExecutor.Next |
| 2024-04-08 08:41:47.359240 | table scan table: user, range: [[-inf,+inf]] | | *executor.TableReaderExecutor.Next |
| 2024-04-08 08:41:47.359242 | execute done, ReturnRow: 1, ModifyRow: 0 | | trace |
| 2024-04-08 08:41:47.359252 | execute done, modify row: 0 | | trace |
+----------------------------+--------------------------------------------------------+------+------------------------------------+
14 rows in set (0.0008 sec)
MySQL 兼容性
TRACE 语句是 TiDB 对 MySQL 语法的扩展。