SET @start_global_value = @@global.optimizer_trace_features;
SELECT @start_global_value;
@start_global_value
greedy_search=on,range_optimizer=on,dynamic_range=on,repeated_subselect=on
select @@global.optimizer_trace_features;
@@global.optimizer_trace_features
greedy_search=on,range_optimizer=on,dynamic_range=on,repeated_subselect=on
select @@session.optimizer_trace_features;
@@session.optimizer_trace_features
greedy_search=on,range_optimizer=on,dynamic_range=on,repeated_subselect=on
show global variables like 'optimizer_trace_features';
Variable_name	Value
optimizer_trace_features	greedy_search=on,range_optimizer=on,dynamic_range=on,repeated_subselect=on
show session variables like 'optimizer_trace_features';
Variable_name	Value
optimizer_trace_features	greedy_search=on,range_optimizer=on,dynamic_range=on,repeated_subselect=on
select * from information_schema.global_variables where variable_name='optimizer_trace_features';
VARIABLE_NAME	VARIABLE_VALUE
OPTIMIZER_TRACE_FEATURES	greedy_search=on,range_optimizer=on,dynamic_range=on,repeated_subselect=on
select * from information_schema.session_variables where variable_name='optimizer_trace_features';
VARIABLE_NAME	VARIABLE_VALUE
OPTIMIZER_TRACE_FEATURES	greedy_search=on,range_optimizer=on,dynamic_range=on,repeated_subselect=on
set global optimizer_trace_features=2;
select @@global.optimizer_trace_features;
@@global.optimizer_trace_features
greedy_search=off,range_optimizer=on,dynamic_range=off,repeated_subselect=off
set session optimizer_trace_features=2;
select @@session.optimizer_trace_features;
@@session.optimizer_trace_features
greedy_search=off,range_optimizer=on,dynamic_range=off,repeated_subselect=off
set global optimizer_trace_features=0;
select @@global.optimizer_trace_features;
@@global.optimizer_trace_features
greedy_search=off,range_optimizer=off,dynamic_range=off,repeated_subselect=off
set session optimizer_trace_features=0;
select @@session.optimizer_trace_features;
@@session.optimizer_trace_features
greedy_search=off,range_optimizer=off,dynamic_range=off,repeated_subselect=off
set session optimizer_trace_features=default;
select @@session.optimizer_trace_features;
@@session.optimizer_trace_features
greedy_search=off,range_optimizer=off,dynamic_range=off,repeated_subselect=off
set global optimizer_trace_features=1.1;
ERROR 42000: Incorrect argument type to variable 'optimizer_trace_features'
set global optimizer_trace_features=1e1;
ERROR 42000: Incorrect argument type to variable 'optimizer_trace_features'
set session optimizer_trace_features="foobar";
ERROR 42000: Variable 'optimizer_trace_features' can't be set to the value of 'foobar'
SET @@global.optimizer_trace_features = @start_global_value;
SELECT @@global.optimizer_trace_features;
@@global.optimizer_trace_features
greedy_search=on,range_optimizer=on,dynamic_range=on,repeated_subselect=on