SET @start_global_value = @@global.thread_cache_size;
SELECT @start_global_value;
@start_global_value
0
select @@global.thread_cache_size;
@@global.thread_cache_size
0
select @@session.thread_cache_size;
ERROR HY000: Variable 'thread_cache_size' is a GLOBAL variable
show global variables like 'thread_cache_size';
Variable_name	Value
thread_cache_size	0
show session variables like 'thread_cache_size';
Variable_name	Value
thread_cache_size	0
select * from information_schema.global_variables where variable_name='thread_cache_size';
VARIABLE_NAME	VARIABLE_VALUE
THREAD_CACHE_SIZE	0
select * from information_schema.session_variables where variable_name='thread_cache_size';
VARIABLE_NAME	VARIABLE_VALUE
THREAD_CACHE_SIZE	0
set global thread_cache_size=1;
select @@global.thread_cache_size;
@@global.thread_cache_size
1
select * from information_schema.global_variables where variable_name='thread_cache_size';
VARIABLE_NAME	VARIABLE_VALUE
THREAD_CACHE_SIZE	1
select * from information_schema.session_variables where variable_name='thread_cache_size';
VARIABLE_NAME	VARIABLE_VALUE
THREAD_CACHE_SIZE	1
set session thread_cache_size=1;
ERROR HY000: Variable 'thread_cache_size' is a GLOBAL variable and should be set with SET GLOBAL
set global thread_cache_size=1.1;
ERROR 42000: Incorrect argument type to variable 'thread_cache_size'
set global thread_cache_size=1e1;
ERROR 42000: Incorrect argument type to variable 'thread_cache_size'
set global thread_cache_size="foo";
ERROR 42000: Incorrect argument type to variable 'thread_cache_size'
set global thread_cache_size=0;
select @@global.thread_cache_size;
@@global.thread_cache_size
0
set global thread_cache_size=cast(-1 as unsigned int);
Warnings:
Warning	1292	Truncated incorrect thread_cache_size value: '18446744073709551615'
select @@global.thread_cache_size;
@@global.thread_cache_size
16384
SET @@global.thread_cache_size = @start_global_value;
SELECT @@global.thread_cache_size;
@@global.thread_cache_size
0