79.如何获取当前连接id的线程id?

以下演示是在mysql8.0.25版本中

1. PS_CURRENT_THREAD_ID()

root@mysqldb 21:46:  [(none)]> \s;
--------------
mysql  Ver 8.0.25 for Linux on x86_64 (MySQL Community Server - GPL)

Connection id:          10      #这里可以看到当前的连接id是10
Current database:
Current user:           root@localhost
SSL:                    Not in use
Current pager:          stdout
Using outfile:          ''
Using delimiter:        ;
Server version:         8.0.25 MySQL Community Server - GPL
Protocol version:       10
Connection:             Localhost via UNIX socket
Server characterset:    utf8mb4
Db     characterset:    utf8mb4
Client characterset:    utf8mb4
Conn.  characterset:    utf8mb4
UNIX socket:            /data/mysql/3306/data/mysql_3306.sock
Uptime:                 10 min 47 sec

Threads: 3  Questions: 327  Slow queries: 0  Opens: 165  Flush tables: 3  Open tables: 84  Queries per second avg: 0.505
--------------
root@mysqldb 21:46:  [(none)]>  select ps_current_thread_id();
+------------------------+
| ps_current_thread_id() |
+------------------------+
|                     52 |   # 这里可以看到连接id对应的mysql的线程id是52.
+------------------------+

2.PS_THREAD_ID(proceslist_id) 

root@mysqldb 21:49:  [(none)]> select ps_thread_id(10);
+------------------+
| ps_thread_id(10) |
+------------------+
|               52 |
+------------------+
1 row in set (0.00 sec)

　　这里也可以通过连接id，用函数ps_thread_id(),查看到它的线程id.

3. 几张关于连接的表或者视图

　　其中有threads表，sys.processlist或者sys.session视图

　　thread表这里就不说了，主要看看这两张视图，其实这两张视图的字段信息是完全一样的。

　　这里就展示一下：

root@mysqldb 21:40:  [(none)]> select * from sys.processlist where thd_id=50 \G;
*************************** 1. row ***************************
                thd_id: 50
               conn_id: 8
                  user: root@localhost
                    db: test
               command: Sleep
                 state: NULL
                  time: 51
     current_statement: NULL
     statement_latency: NULL
              progress: NULL
          lock_latency: 355.00 us
         rows_examined: 4   #扫描的行数
             rows_sent: 4
         rows_affected: 0
            tmp_tables: 0
       tmp_disk_tables: 0
             full_scan: YES
        last_statement: select * from t    #这里还展示了最新执行的动作。
last_statement_latency: 1.96 ms
        current_memory: 1.03 MiB    #当前该线程占用的内存大小(这个挺重要的)
             last_wait: NULL
     last_wait_latency: NULL
                source: NULL
           trx_latency: 83.68 us
             trx_state: COMMITTED
        trx_autocommit: YES
                   pid: 4126
          program_name: mysql