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0dfe3a8dfb
Problem: Table_locks_waited value may depend on general logging. Fix: switch general logging off.
165 lines
4.6 KiB
Plaintext
165 lines
4.6 KiB
Plaintext
flush status;
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show status like 'Table_lock%';
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Variable_name Value
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Table_locks_immediate 1
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Table_locks_waited 0
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select * from information_schema.session_status where variable_name like 'Table_lock%';
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VARIABLE_NAME VARIABLE_VALUE
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TABLE_LOCKS_IMMEDIATE 2
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TABLE_LOCKS_WAITED 0
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SET SQL_LOG_BIN=0;
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set @old_general_log = @@global.general_log;
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set global general_log = 'OFF';
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drop table if exists t1;
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create table t1(n int) engine=myisam;
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insert into t1 values(1);
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lock tables t1 read;
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unlock tables;
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lock tables t1 read;
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update t1 set n = 3;
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unlock tables;
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show status like 'Table_locks_waited';
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Variable_name Value
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Table_locks_waited 1
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drop table t1;
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set global general_log = @old_general_log;
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select 1;
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1
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1
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show status like 'last_query_cost';
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Variable_name Value
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Last_query_cost 0.000000
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create table t1 (a int);
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insert into t1 values (1),(2),(3),(4),(5),(6),(7),(8),(9),(10);
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insert into t1 values (1),(2),(3),(4),(5),(6),(7),(8),(9),(10);
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insert into t1 values (1),(2),(3),(4),(5),(6),(7),(8),(9),(10);
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insert into t1 values (1),(2),(3),(4),(5),(6),(7),(8),(9),(10);
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insert into t1 values (1),(2),(3),(4),(5),(6),(7),(8),(9),(10);
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select * from t1 where a=6;
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a
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6
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6
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6
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6
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6
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show status like 'last_query_cost';
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Variable_name Value
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Last_query_cost 12.084449
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show status like 'last_query_cost';
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Variable_name Value
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Last_query_cost 12.084449
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select 1;
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1
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1
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show status like 'last_query_cost';
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Variable_name Value
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Last_query_cost 0.000000
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drop table t1;
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FLUSH STATUS;
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SHOW STATUS LIKE 'max_used_connections';
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Variable_name Value
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Max_used_connections 1
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SELECT * FROM INFORMATION_SCHEMA.SESSION_STATUS WHERE VARIABLE_NAME LIKE 'max_used_connections';
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VARIABLE_NAME VARIABLE_VALUE
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MAX_USED_CONNECTIONS 1
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SET @save_thread_cache_size=@@thread_cache_size;
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SET GLOBAL thread_cache_size=3;
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SHOW STATUS LIKE 'max_used_connections';
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Variable_name Value
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Max_used_connections 3
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SELECT * FROM INFORMATION_SCHEMA.SESSION_STATUS WHERE VARIABLE_NAME LIKE 'max_used_connections';
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VARIABLE_NAME VARIABLE_VALUE
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MAX_USED_CONNECTIONS 3
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FLUSH STATUS;
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SHOW STATUS LIKE 'max_used_connections';
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Variable_name Value
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Max_used_connections 2
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SELECT * FROM INFORMATION_SCHEMA.SESSION_STATUS WHERE VARIABLE_NAME LIKE 'max_used_connections';
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VARIABLE_NAME VARIABLE_VALUE
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MAX_USED_CONNECTIONS 2
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SHOW STATUS LIKE 'max_used_connections';
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Variable_name Value
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Max_used_connections 3
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SELECT * FROM INFORMATION_SCHEMA.SESSION_STATUS WHERE VARIABLE_NAME LIKE 'max_used_connections';
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VARIABLE_NAME VARIABLE_VALUE
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MAX_USED_CONNECTIONS 3
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SHOW STATUS LIKE 'max_used_connections';
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Variable_name Value
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Max_used_connections 4
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SELECT * FROM INFORMATION_SCHEMA.SESSION_STATUS WHERE VARIABLE_NAME LIKE 'max_used_connections';
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VARIABLE_NAME VARIABLE_VALUE
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MAX_USED_CONNECTIONS 4
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SET GLOBAL thread_cache_size=@save_thread_cache_size;
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CREATE TABLE t1 ( a INT );
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INSERT INTO t1 VALUES (1), (2);
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SELECT a FROM t1 LIMIT 1;
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a
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1
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SHOW SESSION STATUS LIKE 'Last_query_cost';
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Variable_name Value
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Last_query_cost 2.402418
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EXPLAIN SELECT a FROM t1;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 ALL NULL NULL NULL NULL 2
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SHOW SESSION STATUS LIKE 'Last_query_cost';
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Variable_name Value
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Last_query_cost 2.402418
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SELECT a FROM t1 UNION SELECT a FROM t1 ORDER BY a;
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a
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1
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2
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SHOW SESSION STATUS LIKE 'Last_query_cost';
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Variable_name Value
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Last_query_cost 0.000000
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EXPLAIN SELECT a FROM t1 UNION SELECT a FROM t1 ORDER BY a;
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id select_type table type possible_keys key key_len ref rows Extra
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1 PRIMARY t1 ALL NULL NULL NULL NULL 2
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2 UNION t1 ALL NULL NULL NULL NULL 2
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NULL UNION RESULT <union1,2> ALL NULL NULL NULL NULL NULL Using filesort
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SHOW SESSION STATUS LIKE 'Last_query_cost';
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Variable_name Value
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Last_query_cost 0.000000
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SELECT a IN (SELECT a FROM t1) FROM t1 LIMIT 1;
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a IN (SELECT a FROM t1)
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1
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SHOW SESSION STATUS LIKE 'Last_query_cost';
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Variable_name Value
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Last_query_cost 0.000000
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SELECT (SELECT a FROM t1 LIMIT 1) x FROM t1 LIMIT 1;
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x
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1
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SHOW SESSION STATUS LIKE 'Last_query_cost';
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Variable_name Value
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Last_query_cost 0.000000
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SELECT * FROM t1 a, t1 b LIMIT 1;
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a a
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1 1
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SHOW SESSION STATUS LIKE 'Last_query_cost';
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Variable_name Value
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Last_query_cost 4.805836
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DROP TABLE t1;
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show status like 'com_show_status';
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Variable_name Value
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Com_show_status 3
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show status like 'hand%write%';
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Variable_name Value
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Handler_write 5
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show status like '%tmp%';
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Variable_name Value
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Created_tmp_disk_tables 0
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Created_tmp_files 0
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Created_tmp_tables 0
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show status like 'hand%write%';
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Variable_name Value
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Handler_write 7
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show status like '%tmp%';
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Variable_name Value
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Created_tmp_disk_tables 0
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Created_tmp_files 0
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Created_tmp_tables 0
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show status like 'com_show_status';
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Variable_name Value
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Com_show_status 8
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rnd_diff tmp_table_diff
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20 8
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