maria-discuss team mailing list archive

[Sergei Golubchik <serg@xxxxxxxxxxx>]

Hi, Peter!

On Jul 13, Peter Laursen wrote:
>  -- MariaDB 10.2.7
> CREATE TABLE `jsontst`( `id` INT NOT NULL AUTO_INCREMENT, `str` JSON,
> PRIMARY KEY (`id`) ) ENGINE=Aria CHARSET=latin1;
> SHOW CREATE TABLE `jsontst`;
> /* returns
> CREATE TABLE `jsontst2` (
>   `id` int(11) NOT NULL AUTO_INCREMENT,
>   `str` text DEFAULT NULL,
>   PRIMARY KEY (`id`)
> ) ENGINE=Aria DEFAULT CHARSET=latin1 PAGE_CHECKSUM=1
> */
> 
> readings:
> https://jira.mariadb.org/browse/MDEV-9144
> https://bugs.mysql.com/bug.php?id=86875
> 
> As you see except for JSON in MariaDB just being a synonym of TEXT there
> are two more significant differences
> 1) length: in MySQL JSON has the lenght of a LONGTEXT - in MariaDB it is a
> (plain) TEXT
> 2) encoding: in MySQL the utf8mb4 character set is enforced for JSON data -
> in MariaDB you may specify any character set.
> 
> I think in particular 2nd point could cause problems (unicode
> garbling) when loading a dump with JSON data from MySQL. Basically
> because latin1 is still default character set in MariaDB.
> 
> Are you aware of the 2 differences? I think the major reason for
> introducing JSON in MariaDB is compability concerns with MySQL.  But
> the 2 points here are IMO incompabilites that could have been avoided?

JSON functions were added for SQL Standard and for MySQL compatibility.

But JSON alias for TEXT - it was only for MySQL compatibility, no other
reasons. So you're right, these issues should be fixed.

1. LONGTEXT - no questions here, we'll fix it.

2. charset. If one would write

     col1 JSON CHARACTER SET latin1

That'll be an error, right?

3. I could make JSON to imply validity checks too.

     col1 JSON

being equal to

     col1 LONGTEXT CHARACTER SET utf8mb4 CHECK(JSON_VALID(col1))

is it what users would expect for compatibility reasons?

Regards,
Sergei
Chief Architect MariaDB
and security@xxxxxxxxxxx