Details
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Bug
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Status: Closed (View Workflow)
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Major
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Resolution: Won't Fix
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10.1.34
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None
Description
The documentation for TRUNCATE TABLE says the following:
TRUNCATE TABLE is faster than DELETE, because it drops and re-creates a table. With XtraDB/InnoDB, this is faster if the innodb_file_per_table variable is ON (the default since MariaDB 5.5).
https://mariadb.com/kb/en/library/truncate-table/
What is the basis for the statement that it should be faster if innodb_file_per_table=ON is set? This does not seem to be true for a relatively small table with only 50k rows.
For example, let's create a table and populate it with the following:
CREATE TABLE test_table (
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id int NOT NULL PRIMARY KEY AUTO_INCREMENT,
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val int
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);
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DELIMITER $$
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CREATE PROCEDURE prepare_data(num_rows int)
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BEGIN
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DECLARE i INT DEFAULT 0;
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WHILE i < num_rows DO
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INSERT INTO test_table (val) VALUES (FLOOR(RAND() * 1000000));
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SET i = i + 1;
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END WHILE;
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END$$
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DELIMITER ;
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CALL prepare_data(50000);
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Then let's run the following statements with both innodb_file_per_table set to ON and OFF:
SHOW GLOBAL VARIABLES LIKE 'innodb_file_per_table';
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CREATE TABLE truncate_test AS SELECT * FROM test_table;
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SET profiling = 1;
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TRUNCATE TABLE truncate_test;
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SHOW PROFILES;
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SHOW PROFILE ALL;
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DROP TABLE truncate_test;
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Here are the results:
MariaDB [db1]> SHOW GLOBAL VARIABLES LIKE 'innodb_file_per_table';
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+-----------------------+-------+
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| Variable_name | Value |
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+-----------------------+-------+
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| innodb_file_per_table | ON |
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+-----------------------+-------+
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1 row in set (0.00 sec)
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MariaDB [db1]> CREATE TABLE truncate_test AS SELECT * FROM test_table;
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Query OK, 50000 rows affected (0.24 sec)
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Records: 50000 Duplicates: 0 Warnings: 0
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MariaDB [db1]> SET profiling = 1;
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Query OK, 0 rows affected (0.00 sec)
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MariaDB [db1]> TRUNCATE TABLE truncate_test;
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Query OK, 0 rows affected (0.01 sec)
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MariaDB [db1]> SHOW PROFILES;
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+----------+------------+------------------------------+
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| Query_ID | Duration | Query |
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+----------+------------+------------------------------+
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| 1 | 0.01077308 | TRUNCATE TABLE truncate_test |
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+----------+------------+------------------------------+
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1 row in set (0.00 sec)
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MariaDB [db1]> SHOW PROFILE ALL;
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+----------------------+----------+----------+------------+-------------------+---------------------+--------------+---------------+---------------+-------------------+-------------------+-------------------+-------+-----------------------+--------------+-------------+
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| Status | Duration | CPU_user | CPU_system | Context_voluntary | Context_involuntary | Block_ops_in | Block_ops_out | Messages_sent | Messages_received | Page_faults_major | Page_faults_minor | Swaps | Source_function | Source_file | Source_line |
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+----------------------+----------+----------+------------+-------------------+---------------------+--------------+---------------+---------------+-------------------+-------------------+-------------------+-------+-----------------------+--------------+-------------+
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| starting | 0.000017 | 0.000004 | 0.000007 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | NULL | NULL | NULL |
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| Opening tables | 0.000007 | 0.000002 | 0.000004 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | open_ltable | sql_base.cc | 5176 |
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| System lock | 0.000002 | 0.000001 | 0.000002 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | mysql_lock_tables | lock.cc | 308 |
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| Table lock | 0.000002 | 0.000001 | 0.000001 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | mysql_lock_tables | lock.cc | 313 |
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| Opening tables | 0.000002 | 0.000000 | 0.000001 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | mysql_lock_tables | lock.cc | 328 |
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| After opening tables | 0.000012 | 0.000005 | 0.000009 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | open_ltable | sql_base.cc | 5245 |
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| closing tables | 0.000002 | 0.000001 | 0.000001 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | close_thread_tables | sql_base.cc | 919 |
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| Unlocking tables | 0.000015 | 0.000005 | 0.000010 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | mysql_unlock_tables | lock.cc | 396 |
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| checking permissions | 0.000021 | 0.000008 | 0.000014 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | check_access | sql_parse.cc | 6154 |
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| Opening tables | 0.000170 | 0.004876 | 0.000000 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | open_tables | sql_base.cc | 4532 |
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| After opening tables | 0.000004 | 0.000000 | 0.000000 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | open_tables | sql_base.cc | 4779 |
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| System lock | 0.000003 | 0.000000 | 0.000000 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | mysql_lock_tables | lock.cc | 308 |
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| Table lock | 0.010468 | 0.000000 | 0.000000 | 21 | 0 | 8 | 256 | 0 | 0 | 0 | 0 | 0 | mysql_lock_tables | lock.cc | 313 |
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| Writing to binlog | 0.000018 | 0.000000 | 0.000000 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | write_bin_log | sql_table.cc | 1969 |
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| query end | 0.000005 | 0.000000 | 0.000000 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | mysql_execute_command | sql_parse.cc | 5706 |
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| closing tables | 0.000002 | 0.000000 | 0.000000 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | close_thread_tables | sql_base.cc | 919 |
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| Unlocking tables | 0.000007 | 0.000000 | 0.000000 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | mysql_unlock_tables | lock.cc | 396 |
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| freeing items | 0.000003 | 0.000000 | 0.000000 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | mysql_parse | sql_parse.cc | 7466 |
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| updating status | 0.000008 | 0.000000 | 0.000000 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | dispatch_command | sql_parse.cc | 1954 |
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| cleaning up | 0.000002 | 0.000000 | 0.000000 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | dispatch_command | sql_parse.cc | 1973 |
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+----------------------+----------+----------+------------+-------------------+---------------------+--------------+---------------+---------------+-------------------+-------------------+-------------------+-------+-----------------------+--------------+-------------+
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20 rows in set (0.00 sec)
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MariaDB [db1]> DROP TABLE truncate_test;
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Query OK, 0 rows affected (0.01 sec)
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MariaDB [db1]> SHOW GLOBAL VARIABLES LIKE 'innodb_file_per_table';
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+-----------------------+-------+
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| Variable_name | Value |
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+-----------------------+-------+
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| innodb_file_per_table | OFF |
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+-----------------------+-------+
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1 row in set (0.00 sec)
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MariaDB [db1]> CREATE TABLE truncate_test AS SELECT * FROM test_table;
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Query OK, 50000 rows affected (0.16 sec)
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Records: 50000 Duplicates: 0 Warnings: 0
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MariaDB [db1]> SET profiling = 1;
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Query OK, 0 rows affected (0.00 sec)
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MariaDB [db1]> TRUNCATE TABLE truncate_test;
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Query OK, 0 rows affected (0.00 sec)
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MariaDB [db1]> SHOW PROFILES;
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+----------+------------+------------------------------+
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| Query_ID | Duration | Query |
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+----------+------------+------------------------------+
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| 1 | 0.00474932 | TRUNCATE TABLE truncate_test |
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+----------+------------+------------------------------+
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1 row in set (0.00 sec)
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MariaDB [db1]> SHOW PROFILE ALL;
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+----------------------+----------+----------+------------+-------------------+---------------------+--------------+---------------+---------------+-------------------+-------------------+-------------------+-------+-----------------------+--------------+-------------+
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| Status | Duration | CPU_user | CPU_system | Context_voluntary | Context_involuntary | Block_ops_in | Block_ops_out | Messages_sent | Messages_received | Page_faults_major | Page_faults_minor | Swaps | Source_function | Source_file | Source_line |
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+----------------------+----------+----------+------------+-------------------+---------------------+--------------+---------------+---------------+-------------------+-------------------+-------------------+-------+-----------------------+--------------+-------------+
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| starting | 0.000016 | 0.000005 | 0.000006 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | NULL | NULL | NULL |
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| Opening tables | 0.000008 | 0.000004 | 0.000004 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | open_ltable | sql_base.cc | 5176 |
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| System lock | 0.000002 | 0.000001 | 0.000001 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | mysql_lock_tables | lock.cc | 308 |
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| Table lock | 0.000002 | 0.000001 | 0.000001 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | mysql_lock_tables | lock.cc | 313 |
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| Opening tables | 0.000002 | 0.000001 | 0.000001 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | mysql_lock_tables | lock.cc | 328 |
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| After opening tables | 0.000015 | 0.000008 | 0.000008 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | open_ltable | sql_base.cc | 5245 |
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| closing tables | 0.000002 | 0.000001 | 0.000001 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | close_thread_tables | sql_base.cc | 919 |
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| Unlocking tables | 0.000016 | 0.000008 | 0.000008 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | mysql_unlock_tables | lock.cc | 396 |
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| checking permissions | 0.000020 | 0.000010 | 0.000010 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | check_access | sql_parse.cc | 6154 |
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| Opening tables | 0.000147 | 0.000074 | 0.000075 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | open_tables | sql_base.cc | 4532 |
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| After opening tables | 0.000005 | 0.000002 | 0.000001 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | open_tables | sql_base.cc | 4779 |
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| System lock | 0.000002 | 0.000001 | 0.000002 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | mysql_lock_tables | lock.cc | 308 |
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| Table lock | 0.004469 | 0.001860 | 0.000000 | 11 | 1 | 0 | 40 | 0 | 0 | 0 | 5 | 0 | mysql_lock_tables | lock.cc | 313 |
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| Writing to binlog | 0.000017 | 0.000000 | 0.000000 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | write_bin_log | sql_table.cc | 1969 |
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| query end | 0.000004 | 0.000000 | 0.000000 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | mysql_execute_command | sql_parse.cc | 5706 |
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| closing tables | 0.000003 | 0.000000 | 0.000000 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | close_thread_tables | sql_base.cc | 919 |
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| Unlocking tables | 0.000008 | 0.000000 | 0.000000 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | mysql_unlock_tables | lock.cc | 396 |
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| freeing items | 0.000003 | 0.000000 | 0.000000 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | mysql_parse | sql_parse.cc | 7466 |
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| updating status | 0.000006 | 0.000000 | 0.000000 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | dispatch_command | sql_parse.cc | 1954 |
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| cleaning up | 0.000002 | 0.000000 | 0.000000 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | dispatch_command | sql_parse.cc | 1973 |
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+----------------------+----------+----------+------------+-------------------+---------------------+--------------+---------------+---------------+-------------------+-------------------+-------------------+-------+-----------------------+--------------+-------------+
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20 rows in set (0.00 sec)
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MariaDB [db1]> DROP TABLE truncate_test;
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Query OK, 0 rows affected (0.00 sec)
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It seems to be consistently faster with innodb_file_per_table=OFF set. The difference seems to be in the Table lock state, and there seems to be a difference in the Block_ops_out value.
Is this a bug, or is the statement in the documentation incorrect, or is there an exception to this rule for relatively small tables?
Attachments
Issue Links
- relates to
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- Closed
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- Closed
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MDEV-17492 Benchmark AHI to find cases where it's useful
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- Closed
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- Closed
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