who is truncating columns? On 3/1/15, 3:27 PM, "Sergei Golubchik" <serg@mariadb.org> wrote:
Hi, Tom!
On Mar 01, Tom Worster wrote:
I discovered this showstopper on Friday while working with real data in development of a new app. I managed to narrow it down today and filed the bug report.
https://mariadb.atlassian.net/browse/MDEV-7650
Looks like Maria saves an illegally formatted dyncol string if a dynamic column is longer than 64kB and is not alphabetically last by name among the dynamic column in the blob.
Tbh, even is this were fixed tomorrow so I could proceed with my work, I'm not sure I would use dyncols. My confidence in the feature has been shaken. It's a pity because the Active Record ORM extension I wrote was working.
You could've paid attention to warnings from your test case:
=========== MariaDB [test]> insert into t (a, b, dcols) values (1, 'two', column_create('one', 1, 'css', @txt)); Query OK, 1 row affected, 1 warning (0.00 sec)
Warning (Code 1265): Data truncated for column 'dcols' at row 1 ===========
Indeed, blob size is limited by 64K. Another test case for your bug is:
=========== MariaDB [test]> select length(column_create('one', 1, 'txt', @txt)); +----------------------------------------------+ | length(column_create('one', 1, 'css', @txt)) | +----------------------------------------------+ | 65563 | +----------------------------------------------+ 1 row in set (0.00 sec)
MariaDB [test]> select column_check(left(column_create('one', 1, 'txt', @txt), 65535)); +-----------------------------------------------------------------+ | column_check(left(column_create('one', 1, 'txt', @txt), 65535)) | +-----------------------------------------------------------------+ | 1 | +-----------------------------------------------------------------+ 1 row in set (0.00 sec)
MariaDB [test]> select column_check(left(column_create('one', 1, 'css', @txt), 65535)); +-----------------------------------------------------------------+ | column_check(left(column_create('one', 1, 'css', @txt), 65535)) | +-----------------------------------------------------------------+ | 0 | +-----------------------------------------------------------------+ 1 row in set (0.00 sec) ===========
So the bug is that column_check() doesn't always detects that the dyncol was truncated.
Either way, even if column_check() returns 1, you probably shouldn't use truncated dynamic columns in your application :)
Use LONGBLOB instead.
Regards, Sergei