Compare behavior in MySQL 5.5, MariaDB 5.5.41 and MariaDB 5.5.42:
MySQL 5.5
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elenst@wheezy-64:~/git/mysql-5.5/mysql-test$ ls -l | grep var
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elenst@wheezy-64:~/git/mysql-5.5/mysql-test$
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elenst@wheezy-64:~/git/mysql-5.5/mysql-test$ ls -l /dev/shm/ | grep var
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elenst@wheezy-64:~/git/mysql-5.5/mysql-test$
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elenst@wheezy-64:~/git/mysql-5.5/mysql-test$ perl ./mtr main.1st --mem
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Logging: ./mtr main.1st --mem
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MySQL Version 5.5.42
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...
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Creating var directory '/data/repo/git/mysql-5.5/mysql-test/var'...
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- symlinking 'var' to '/dev/shm/var_auto_UXHl'
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...
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Completed: All 1 tests were successful.
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elenst@wheezy-64:~/git/mysql-5.5/mysql-test$ ls -l | grep var
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lrwxrwxrwx 1 elenst disk 22 Feb 27 02:52 var -> /dev/shm/var_auto_UXHl
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elenst@wheezy-64:~/git/mysql-5.5/mysql-test$ ls -l /dev/shm/ | grep var
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drwxr-xr-x 8 elenst disk 180 Feb 27 02:52 var_auto_UXHl
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elenst@wheezy-64:~/git/mysql-5.5/mysql-test$ perl ./mtr main.1st --mem
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Logging: ./mtr main.1st --mem
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MySQL Version 5.5.42
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...
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Creating var directory '/data/repo/git/mysql-5.5/mysql-test/var'...
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- symlinking 'var' to '/dev/shm/var_auto_uUQE'
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...
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Completed: All 1 tests were successful.
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elenst@wheezy-64:~/git/mysql-5.5/mysql-test$ ls -l | grep var
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lrwxrwxrwx 1 elenst disk 22 Feb 27 02:52 var -> /dev/shm/var_auto_uUQE
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elenst@wheezy-64:~/git/mysql-5.5/mysql-test$ ls -l /dev/shm/ | grep var
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drwxr-xr-x 8 elenst disk 180 Feb 27 02:52 var_auto_uUQE
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This is good behavior: a new folder in /dev/shm gets created, the old one gets removed, var points at the new one.
MariaDB 5.5.41
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elenst@wheezy-64:/data/releases/mariadb-5.5.41-linux-x86_64/mysql-test$ ls -l | grep var
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elenst@wheezy-64:/data/releases/mariadb-5.5.41-linux-x86_64/mysql-test$ ls -l /dev/shm/ | grep var
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elenst@wheezy-64:/data/releases/mariadb-5.5.41-linux-x86_64/mysql-test$ perl ./mtr main.1st --mem
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Logging: ./mtr main.1st --mem
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vardir: /data/releases/mariadb-5.5.41-linux-x86_64/mysql-test/var
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Removing old var directory...
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Creating var directory '/data/releases/mariadb-5.5.41-linux-x86_64/mysql-test/var'...
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- symlinking 'var' to '/dev/shm/var_auto_frKD'
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Checking supported features...
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...
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Completed: All 1 tests were successful.
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elenst@wheezy-64:/data/releases/mariadb-5.5.41-linux-x86_64/mysql-test$ ls -l | grep var
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lrwxrwxrwx 1 elenst disk 22 Feb 27 02:56 var -> /dev/shm/var_auto_frKD
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elenst@wheezy-64:/data/releases/mariadb-5.5.41-linux-x86_64/mysql-test$ ls -l /dev/shm/ | grep var
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drwxr-xr-x 8 elenst disk 180 Feb 27 02:56 var_auto_frKD
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elenst@wheezy-64:/data/releases/mariadb-5.5.41-linux-x86_64/mysql-test$ perl ./mtr main.1st --mem
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Logging: ./mtr main.1st --mem
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vardir: /run/shm/var_auto_frKD
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Checking leftover processes...
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Removing old var directory...
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Creating var directory '/run/shm/var_auto_frKD'...
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Checking supported features...
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MariaDB Version 5.5.41-MariaDB
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...
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Completed: All 1 tests were successful.
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elenst@wheezy-64:/data/releases/mariadb-5.5.41-linux-x86_64/mysql-test$ ls -l | grep var
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lrwxrwxrwx 1 elenst disk 22 Feb 27 02:56 var -> /dev/shm/var_auto_frKD
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elenst@wheezy-64:/data/releases/mariadb-5.5.41-linux-x86_64/mysql-test$ ls -l /dev/shm/ | grep var
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drwxr-xr-x 8 elenst disk 180 Feb 27 02:56 var_auto_frKD
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drwx------ 2 elenst disk 40 Feb 27 02:56 var_auto_nlxl
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It's bad behavior: a new folder gets created, the old one is kept, var points at the old one. Eventually there will be lots of folders in /dev/shm, but it's only marginally dangerous since they all will be empty.
elenst@wheezy-64:~/git/5.5/mysql-test$ ls -l /dev/shm/ | grep var
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elenst@wheezy-64:~/git/5.5/mysql-test$ perl ./mtr 1st --mem
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Logging: ./mtr 1st --mem
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vardir: /data/repo/git/5.5/mysql-test/var
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Removing old var directory...
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Creating var directory '/data/repo/git/5.5/mysql-test/var'...
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- symlinking 'var' to '/dev/shm/var_auto_aE7b'
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Checking supported features...
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MariaDB Version 5.5.42-MariaDB-debug
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...
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Completed: All 1 tests were successful.
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elenst@wheezy-64:~/git/5.5/mysql-test$ ls -l | grep var
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lrwxrwxrwx 1 elenst disk 22 Feb 27 02:59 var -> /dev/shm/var_auto_aE7b
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elenst@wheezy-64:~/git/5.5/mysql-test$ ls -l /dev/shm/ | grep var
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drwxr-xr-x 9 elenst disk 200 Feb 27 02:59 var_auto_aE7b
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elenst@wheezy-64:~/git/5.5/mysql-test$ perl ./mtr 1st --mem
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Logging: ./mtr 1st --mem
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vardir: /run/shm/var_auto_aE7b
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Checking leftover processes...
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Removing old var directory...
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Creating var directory '/run/shm/var_auto_aE7b'...
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- symlinking 'var' to '/dev/shm/var_auto_Ex34'
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Checking supported features...
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MariaDB Version 5.5.42-MariaDB-debug
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...
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Completed: All 1 tests were successful.
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elenst@wheezy-64:~/git/5.5/mysql-test$ ls -l | grep var
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lrwxrwxrwx 1 elenst disk 22 Feb 27 02:59 var -> /dev/shm/var_auto_aE7b
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elenst@wheezy-64:~/git/5.5/mysql-test$ ls -l /dev/shm/ | grep var
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lrwxrwxrwx 1 elenst disk 22 Feb 27 02:59 var_auto_aE7b -> /dev/shm/var_auto_Ex34
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drwxr-xr-x 9 elenst disk 200 Feb 27 02:59 var_auto_Ex34
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This is awful behavior: a new folder gets created, instead of the old folder a link with the same name points at the new folder, var points at the old folder (now a link). Soon enough the chain becomes too long and further tests refuse to run.
At least the old behavior should be restored. Better still, it should work the way MySQL does.
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