如何使用dbms_sql.add_trace来指定SQL Trace功能跟踪的SQL语句_云原生数据库 PolarDB(PolarDB)-阿里云帮助中心

当loose_sql_trace_type参数设置为DEMAND时，您可以使用dbms_sql.add_trace存储过程来指定SQL Trace功能跟踪的SQL语句。

语法

dbms_sql.add_trace('<schema>', '<query>')

说明

执行该存储过程后，SQL语句中的常量会被自动模板化，匹配该模板的SQL语句会被SQL Trace功能跟踪。

参数说明

参数	说明
schema	Schema名称。
query	具体的SQL语句。

注意事项

当在主节点执行该存储过程时，该操作会被持久化，mysql.sql_sharing表中对应的记录会被删除，并同步至只读节点。
当在只读节点执行该存储过程时，该操作不会被持久化，且仅在该只读节点生效。通过集群地址访问数据库时，模板化后的SQL语句会自动路由至主节点。

示例

指定SQL Trace功能跟踪的SQL语句。示例如下：

call dbms_sql.add_trace('test', 'select * from t where c1 > 1 and c1 < 10');

您可以在mysql.sql_sharing系统表中查询记录。

select * from mysql.sql_sharing\G

执行结果如下：

*************************** 1. row ***************************
         Id: (id number)
     Sql_id: 82t4dswtqjg02
Schema_name: test
       Type: SQL_TRACE
Digest_text: SELECT * FROM `t` WHERE `c1` > ? AND `c1` < ?
    Plan_id: NULL
       Plan: NULL
    Version: 0
Create_time: 2022-11-07 19:05:27.980605
Update_time: 2022-11-07 19:05:27.980605
 Extra_info: NULL

从以上结果可以看出，SQL语句中的常量已经过模板化处理。

执行与模板匹配的SQL语句，如：

select * from  t where c1 > 1 and c1 < 10;
select * from  t where c1 > 1 and c1 < 100;

您可以在information_schema.sql_sharing系统表中查看SQL语句的跟踪信息和执行计划统计信息。

select * from information_schema.sql_sharing\G

执行结果如下：

*************************** 1. row ***************************
              TYPE: SQL
            SQL_ID: 82t4dswtqjg02
       SCHEMA_NAME: test
       DIGEST_TEXT: SELECT * FROM `t` WHERE `c1` > ? AND `c1` < ?
           PLAN_ID: NULL
              PLAN: NULL
        PLAN_EXTRA: NULL
        ERROR_CODE: NULL
            REF_BY: SQL_TRACE(DEMAND)
   FIRST_LOAD_TIME: 2022-11-07 19:05:28
     LAST_HIT_TIME: 2022-11-07 19:17:24
        EXECUTIONS: 2
     SUM_WAIT_TIME: 363
     MIN_WAIT_TIME: 179
     MAX_WAIT_TIME: 184
     SUM_EXEC_TIME: 925
     MIN_EXEC_TIME: 438
     MAX_EXEC_TIME: 487
     SUM_ROWS_SENT: 106
     MIN_ROWS_SENT: 8
     MAX_ROWS_SENT: 98
 SUM_ROWS_EXAMINED: 108
 MIN_ROWS_EXAMINED: 8
 MAX_ROWS_EXAMINED: 100
 SUM_ROWS_AFFECTED: 0
 MIN_ROWS_AFFECTED: 0
 MAX_ROWS_AFFECTED: 0
  SUM_LOGICAL_READ: 122
  MIN_LOGICAL_READ: 19
  MAX_LOGICAL_READ: 103
 SUM_PHY_SYNC_READ: 0
 MIN_PHY_SYNC_READ: 0
 MAX_PHY_SYNC_READ: 0
SUM_PHY_ASYNC_READ: 0
MIN_PHY_ASYNC_READ: 0
MAX_PHY_ASYNC_READ: 0
             EXTRA: {TRACE_ROW_ID:10}
*************************** 2. row ***************************
              TYPE: PLAN
            SQL_ID: 82t4dswtqjg02
       SCHEMA_NAME: test
       DIGEST_TEXT: NULL
           PLAN_ID: 5a4cvp4gjqgfj
              PLAN: /*+ NO_INDEX(`t`@`select#1`) */
        PLAN_EXTRA: {`t`@`select#1`:ALL}
        ERROR_CODE: 0
            REF_BY: SQL_TRACE(DEMAND)
   FIRST_LOAD_TIME: 2022-11-07 19:17:24
     LAST_HIT_TIME: 2022-11-07 19:17:24
        EXECUTIONS: 1
     SUM_WAIT_TIME: 184
     MIN_WAIT_TIME: 184
     MAX_WAIT_TIME: 184
     SUM_EXEC_TIME: 487
     MIN_EXEC_TIME: 487
     MAX_EXEC_TIME: 487
     SUM_ROWS_SENT: 98
     MIN_ROWS_SENT: 98
     MAX_ROWS_SENT: 98
 SUM_ROWS_EXAMINED: 100
 MIN_ROWS_EXAMINED: 100
 MAX_ROWS_EXAMINED: 100
 SUM_ROWS_AFFECTED: 0
 MIN_ROWS_AFFECTED: 0
 MAX_ROWS_AFFECTED: 0
  SUM_LOGICAL_READ: 103
  MIN_LOGICAL_READ: 103
  MAX_LOGICAL_READ: 103
 SUM_PHY_SYNC_READ: 0
 MIN_PHY_SYNC_READ: 0
 MAX_PHY_SYNC_READ: 0
SUM_PHY_ASYNC_READ: 0
MIN_PHY_ASYNC_READ: 0
MAX_PHY_ASYNC_READ: 0
             EXTRA: NULL
*************************** 3. row ***************************
              TYPE: PLAN
            SQL_ID: 82t4dswtqjg02
       SCHEMA_NAME: test
       DIGEST_TEXT: NULL
           PLAN_ID: 463zszw4mbv3w
              PLAN: /*+ INDEX(`t`@`select#1` `i_c1`) */
        PLAN_EXTRA: {`t`@`select#1`:range}
        ERROR_CODE: 0
            REF_BY: SQL_TRACE(DEMAND)
   FIRST_LOAD_TIME: 2022-11-07 19:17:21
     LAST_HIT_TIME: 2022-11-07 19:17:21
        EXECUTIONS: 1
     SUM_WAIT_TIME: 179
     MIN_WAIT_TIME: 179
     MAX_WAIT_TIME: 179
     SUM_EXEC_TIME: 438
     MIN_EXEC_TIME: 438
     MAX_EXEC_TIME: 438
     SUM_ROWS_SENT: 8
     MIN_ROWS_SENT: 8
     MAX_ROWS_SENT: 8
 SUM_ROWS_EXAMINED: 8
 MIN_ROWS_EXAMINED: 8
 MAX_ROWS_EXAMINED: 8
 SUM_ROWS_AFFECTED: 0
 MIN_ROWS_AFFECTED: 0
 MAX_ROWS_AFFECTED: 0
  SUM_LOGICAL_READ: 19
  MIN_LOGICAL_READ: 19
  MAX_LOGICAL_READ: 19
 SUM_PHY_SYNC_READ: 0
 MIN_PHY_SYNC_READ: 0
 MAX_PHY_SYNC_READ: 0
SUM_PHY_ASYNC_READ: 0
MIN_PHY_ASYNC_READ: 0
MAX_PHY_ASYNC_READ: 0
             EXTRA: NULL

结论

从以上结果可以看出，两条SQL语句对应2个执行计划，分别为索引i_c1范围扫描和全表扫描。