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flush status;
show status like 'Table_lock%';
Variable_name Value
Table_locks_immediate 1
Table_locks_waited 0
select * from information_schema.session_status where variable_name like 'Table_lock%';
VARIABLE_NAME VARIABLE_VALUE
TABLE_LOCKS_IMMEDIATE 2
TABLE_LOCKS_WAITED 0
SET SQL_LOG_BIN=0;
set @old_general_log = @@global.general_log;
set global general_log = 'OFF';
drop table if exists t1;
create table t1(n int) engine=myisam;
insert into t1 values(1);
lock tables t1 read;
unlock tables;
lock tables t1 read;
update t1 set n = 3;
unlock tables;
show status like 'Table_locks_waited';
Variable_name Value
Table_locks_waited 1
drop table t1;
set global general_log = @old_general_log;
select 1;
1
1
show status like 'last_query_cost';
Variable_name Value
Last_query_cost 0.000000
create table t1 (a int);
insert into t1 values (1),(2),(3),(4),(5),(6),(7),(8),(9),(10);
insert into t1 values (1),(2),(3),(4),(5),(6),(7),(8),(9),(10);
insert into t1 values (1),(2),(3),(4),(5),(6),(7),(8),(9),(10);
insert into t1 values (1),(2),(3),(4),(5),(6),(7),(8),(9),(10);
insert into t1 values (1),(2),(3),(4),(5),(6),(7),(8),(9),(10);
select * from t1 where a=6;
a
6
6
6
6
6
show status like 'last_query_cost';
Variable_name Value
Last_query_cost 12.084449
show status like 'last_query_cost';
Variable_name Value
Last_query_cost 12.084449
select 1;
1
1
show status like 'last_query_cost';
Variable_name Value
Last_query_cost 0.000000
drop table t1;
FLUSH STATUS;
SHOW STATUS LIKE 'max_used_connections';
Variable_name Value
Max_used_connections 1
SELECT * FROM INFORMATION_SCHEMA.SESSION_STATUS WHERE VARIABLE_NAME LIKE 'max_used_connections';
VARIABLE_NAME VARIABLE_VALUE
MAX_USED_CONNECTIONS 1
SET @save_thread_cache_size=@@thread_cache_size;
SET GLOBAL thread_cache_size=3;
SHOW STATUS LIKE 'max_used_connections';
Variable_name Value
Max_used_connections 3
SELECT * FROM INFORMATION_SCHEMA.SESSION_STATUS WHERE VARIABLE_NAME LIKE 'max_used_connections';
VARIABLE_NAME VARIABLE_VALUE
MAX_USED_CONNECTIONS 3
FLUSH STATUS;
SHOW STATUS LIKE 'max_used_connections';
Variable_name Value
Max_used_connections 2
SELECT * FROM INFORMATION_SCHEMA.SESSION_STATUS WHERE VARIABLE_NAME LIKE 'max_used_connections';
VARIABLE_NAME VARIABLE_VALUE
MAX_USED_CONNECTIONS 2
SHOW STATUS LIKE 'max_used_connections';
Variable_name Value
Max_used_connections 3
SELECT * FROM INFORMATION_SCHEMA.SESSION_STATUS WHERE VARIABLE_NAME LIKE 'max_used_connections';
VARIABLE_NAME VARIABLE_VALUE
MAX_USED_CONNECTIONS 3
SHOW STATUS LIKE 'max_used_connections';
Variable_name Value
Max_used_connections 4
SELECT * FROM INFORMATION_SCHEMA.SESSION_STATUS WHERE VARIABLE_NAME LIKE 'max_used_connections';
VARIABLE_NAME VARIABLE_VALUE
MAX_USED_CONNECTIONS 4
SET GLOBAL thread_cache_size=@save_thread_cache_size;
CREATE TABLE t1 ( a INT );
INSERT INTO t1 VALUES (1), (2);
SELECT a FROM t1 LIMIT 1;
a
1
SHOW SESSION STATUS LIKE 'Last_query_cost';
Variable_name Value
Last_query_cost 2.402418
EXPLAIN SELECT a FROM t1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ALL NULL NULL NULL NULL 2
SHOW SESSION STATUS LIKE 'Last_query_cost';
Variable_name Value
Last_query_cost 2.402418
SELECT a FROM t1 UNION SELECT a FROM t1 ORDER BY a;
a
1
2
SHOW SESSION STATUS LIKE 'Last_query_cost';
Variable_name Value
Last_query_cost 0.000000
EXPLAIN SELECT a FROM t1 UNION SELECT a FROM t1 ORDER BY a;
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 2
2 UNION t1 ALL NULL NULL NULL NULL 2
NULL UNION RESULT <union1,2> ALL NULL NULL NULL NULL NULL Using filesort
SHOW SESSION STATUS LIKE 'Last_query_cost';
Variable_name Value
Last_query_cost 0.000000
SELECT a IN (SELECT a FROM t1) FROM t1 LIMIT 1;
a IN (SELECT a FROM t1)
1
SHOW SESSION STATUS LIKE 'Last_query_cost';
Variable_name Value
Last_query_cost 0.000000
SELECT (SELECT a FROM t1 LIMIT 1) x FROM t1 LIMIT 1;
x
1
SHOW SESSION STATUS LIKE 'Last_query_cost';
Variable_name Value
Last_query_cost 0.000000
SELECT * FROM t1 a, t1 b LIMIT 1;
a a
1 1
SHOW SESSION STATUS LIKE 'Last_query_cost';
Variable_name Value
Last_query_cost 4.805836
DROP TABLE t1;
show status like 'com_show_status';
Variable_name Value
Com_show_status 3
show status like 'hand%write%';
Variable_name Value
Handler_write 5
show status like '%tmp%';
Variable_name Value
Created_tmp_disk_tables 0
Created_tmp_files 0
Created_tmp_tables 0
show status like 'hand%write%';
Variable_name Value
Handler_write 7
show status like '%tmp%';
Variable_name Value
Created_tmp_disk_tables 0
Created_tmp_files 0
Created_tmp_tables 0
show status like 'com_show_status';
Variable_name Value
Com_show_status 8
rnd_diff tmp_table_diff
20 8
show global status like 'Com%function%';
Variable_name Value
Com_alter_function 0
Com_create_function 0
Com_drop_function 0
Com_show_function_code 0
Com_show_function_status 0
create function f1 (x INTEGER) returns integer
begin
declare ret integer;
set ret = x * 10;
return ret;
end //
drop function f1;
show global status like 'Com%function%';
Variable_name Value
Com_alter_function 0
Com_create_function 1
Com_drop_function 1
Com_show_function_code 0
Com_show_function_status 0
SELECT VARIABLE_VALUE INTO @tc FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE VARIABLE_NAME = 'Threads_connected';
SELECT VARIABLE_NAME FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE VARIABLE_NAME = 'Threads_created' AND VARIABLE_VALUE < @tc;
VARIABLE_NAME
SELECT VARIABLE_VALUE INTO @tr FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE VARIABLE_NAME = 'Threads_running';
FLUSH STATUS;
SELECT * FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE VARIABLE_NAME = 'Threads_connected' AND VARIABLE_VALUE < @tc;
VARIABLE_NAME VARIABLE_VALUE
SELECT * FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE VARIABLE_NAME = 'Threads_running' AND VARIABLE_VALUE < @tr;
VARIABLE_NAME VARIABLE_VALUE
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