+1 =) mysql manual sometimes don't help, that's why i really prefer mariadb kb i think that many years ago mysql implement this nontransactional like locks to innodb just to allow guys porting from myisam to innodb using old apps without rewriting the lock/unlock to begin/commit if you are using innodb as transactional you will never use lock/unlock, in my opnion maybe you probably only use locks at filesystem or use get_lock() mysql function or any other IPC function, but be carefull about scalability i don't know what's the 'best' lock server today, all shared locks that i use today i use over a filesystem and network (nfs/smb/others network file system), if get_lock work with galera maybe i could get a try 2014-09-23 6:51 GMT-03:00 Elena Stepanova <elenst@montyprogram.com>:
Hi Federico,
On 23.09.2014 12:50, Federico Razzoli wrote:
Let's make the snippet simpler. Only one table, non-transactional, please look at the difference from what docs say and the real behaviour. If one could explain what UNLOCK TABLES exactly does, it would be great.
MariaDB [test]> SELECT @@in_transaction, @@autocommit; +------------------+--------------+ | @@in_transaction | @@autocommit | +------------------+--------------+ | 0 | 1 | +------------------+--------------+ 1 row in set (0.00 sec)
MariaDB [test]> CREATE OR REPLACE TABLE t (c INT) ENGINE = MEMORY; Query OK, 0 rows affected (0.12 sec)
MariaDB [test]> LOCK TABLE t WRITE; Query OK, 0 rows affected (0.00 sec)
MariaDB [test]> START TRANSACTION; Query OK, 0 rows affected (0.00 sec)
"Beginning a transaction causes table locks acquired with LOCK TABLES to be released, as though you had executed UNLOCK TABLES."
http://dev.mysql.com/doc/refman/5.5/en/commit.html
MariaDB [test]> INSERT INTO t VALUES (1); Query OK, 1 row affected (0.01 sec)
MariaDB [test]> UNLOCK TABLES; Query OK, 0 rows affected (0.00 sec)
So, this UNLOCK is not actually doing anything.
Regards, Elena
MariaDB [test]> SELECT @@in_transaction; +------------------+ | @@in_transaction | +------------------+ | 1 | +------------------+ 1 row in set (0.00 sec)
Regards Federico
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