一个咨询单引发的思考：诚实回答客户的提问
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一个咨询单引发的思考：诚实回答客户的提问
1、概述
这是一个做咨询的单子，具体的工作内容就是回答客户的问题，今天突然给我一个截图，在查询information_schema中一张表，但是没有返回结果集。于是给我发消息询问为什么。使用MySQL 8.0已经有一段时间了，不确定这张表为什么没有结果集返回，于是就给客户说不知道，需要查下资料再回复，并记录了数据库的基本信息。客户也没有多说话，只是等待我的回复，事实上这不是我第一次给客户说我不知道某个问题的具体答案。在客户使用数据库的过程中，会有非常多的问题，有些我甚至从来没有听说过，但这并不影响我和客户的合作，在我长期合作的项目中，咨询项目占了三分之一，一句老话，知之为知之，不知为不知，是知也。最近网络有句话，真诚才是必杀技，我想也是适用的。
2、案例重现以及解决方法
[root@mydb01 ~]# mysql
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 2
Server version: 5.7.44-48-log Percona Server (GPL), Release 48, Revision 497f936a373
Copyright (c) 2009-2023 Percona LLC and/or its affiliates
Copyright (c) 2000, 2023, Oracle and/or its affiliates.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql> select * from information_schema.TABLE_STATISTICS;
Empty set (0.00 sec)
mysql>
mysql> set global userstat=ON;
Query OK, 0 rows affected (0.00 sec)
mysql> select * from information_schema.TABLE_STATISTICS;
Empty set (0.00 sec)
mysql> \q
Bye
[root@mydb01 ~]# sysbench --db-driver=mysql --time=10 --threads=20 --report-interval=5 --mysql-host=127.0.0.1 --mysql-port=3306 --mysql-user=test_user --mysql-password=test_user --mysql-db=test_db --tables=5 --table_size=10000 oltp_read_write --db-ps-mode=disable run
sysbench 1.0.20 (using bundled LuaJIT 2.1.0-beta2)
Running the test with following options:
Number of threads: 20
Report intermediate results every 5 second(s)
Initializing random number generator from current time
Initializing worker threads...
Threads started!
[ 5s ] thds: 20 tps: 409.15 qps: 8233.58 (r/w/o: 5770.28/1641.00/822.30) lat (ms,95%): 75.82 err/s: 0.00 reconn/s: 0.00
[ 10s ] thds: 20 tps: 423.08 qps: 8459.55 (r/w/o: 5922.09/1691.31/846.16) lat (ms,95%): 65.65 err/s: 0.00 reconn/s: 0.00
SQL statistics:
queries performed:
read: 58548
write: 16728
other: 8364
total: 83640
transactions: 4182 (416.80 per sec.)
queries: 83640 (8335.96 per sec.)
ignored errors: 0 (0.00 per sec.)
reconnects: 0 (0.00 per sec.)
General statistics:
total time: 10.0319s
total number of events: 4182
Latency (ms):
min: 4.58
avg: 47.87
max: 295.50
95th percentile: 70.55
sum: 200185.92
Threads fairness:
events (avg/stddev): 209.1000/7.36
execution time (avg/stddev): 10.0093/0.01
[root@mydb01 ~]# mysql
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 23
Server version: 5.7.44-48-log Percona Server (GPL), Release 48, Revision 497f936a373
Copyright (c) 2009-2023 Percona LLC and/or its affiliates
Copyright (c) 2000, 2023, Oracle and/or its affiliates.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql> select * from information_schema.TABLE_STATISTICS;
+--------------+------------+-----------+--------------+------------------------+
| TABLE_SCHEMA | TABLE_NAME | ROWS_READ | ROWS_CHANGED | ROWS_CHANGED_X_INDEXES |
+--------------+------------+-----------+--------------+------------------------+
| test_db | sbtest1 | 349972 | 3292 | 6584 |
| test_db | sbtest4 | 345458 | 3420 | 6840 |
| test_db | sbtest3 | 345751 | 3354 | 6708 |
| test_db | sbtest2 | 355026 | 3402 | 6804 |
| test_db | sbtest5 | 344866 | 3260 | 6520 |
+--------------+------------+-----------+--------------+------------------------+
5 rows in set (0.00 sec)
mysql>
