maria-discuss team mailing list archive

[Roberto Spadim <roberto@xxxxxxxxxxxxx>]

+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@xxxxxxxxxxxxxxxx>:

> 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
>>
>>
>> _______________________________________________
>> Mailing list: https://launchpad.net/~maria-discuss
>> Post to     : maria-discuss@xxxxxxxxxxxxxxxxxxx
>> Unsubscribe : https://launchpad.net/~maria-discuss
>> More help   : https://help.launchpad.net/ListHelp
>>
>>
> _______________________________________________
> Mailing list: https://launchpad.net/~maria-discuss
> Post to     : maria-discuss@xxxxxxxxxxxxxxxxxxx
> Unsubscribe : https://launchpad.net/~maria-discuss
> More help   : https://help.launchpad.net/ListHelp
>



-- 
Roberto Spadim
SPAEmpresarial
Eng. Automação e Controle