max_prepared_stmt_count doesn't take effect

[xuyifangreeneyes]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

set @@global.max_prepared_stmt_count = 2;
prepare stmt1 from 'select ? as num from dual';
prepare stmt2 from 'select ? as num from dual';
prepare stmt3 from 'select ? as num from dual';

2. What did you expect to see? (Required)

mysql> set @@global.max_prepared_stmt_count = 2;
Query OK, 0 rows affected (0.00 sec)

mysql> prepare stmt1 from 'select ? as num from dual';
Query OK, 0 rows affected (0.00 sec)

mysql> prepare stmt2 from 'select ? as num from dual';
Query OK, 0 rows affected (0.00 sec)

mysql> prepare stmt3 from 'select ? as num from dual';
ERROR 1461 (42000): Can't create more than maxPreparedStmtCount statements (current value: 2)

3. What did you see instead (Required)

mysql> set @@global.max_prepared_stmt_count = 2;
Query OK, 0 rows affected (0.01 sec)

mysql> prepare stmt1 from 'select ? as num from dual';
Query OK, 0 rows affected (0.00 sec)

mysql> prepare stmt2 from 'select ? as num from dual';
Query OK, 0 rows affected (0.00 sec)

mysql> prepare stmt3 from 'select ? as num from dual';
Query OK, 0 rows affected (0.00 sec)

4. What is your TiDB version? (Required)

master

[xuyifangreeneyes]

The root cause is that we don't get the global variable correctly.