maria-developers team mailing list archive

[Alexander Barkov <bar@xxxxxxxxxxx>]

Hi Jeremy,

On 11/12/2013 07:09 AM, Jeremy Cole wrote:
> Sergei,
>
> In the process of working through the bugs I've reported re. time
> formats and InnoDB storage formats we noted that there isn't currently
> any way to cause MariaDB to create a *new* Oracle MySQL 5.6-format
> TIMESTAMP/TIME/DATETIME field, and thus there's not really very good
> test coverage of them. Additionally the existence of this difference
> relative to Oracle MySQL is not really desirable.
>
> I would propose adding a new sysvar to control the temporal time format
> e.g. temporal_microsecond_format={mysql|mariadb} which controls whether
> newly created columns are created as Field_*_hires or Field_*f. This
> would especially allow:
>
>  1. Tests to be run in both Oracle MySQL and MariaDB modes.
>  2. A single test to create a column in one format and request
>     conversion to the other.
>  3. A user to convert the format of their existing tables for compatibility.
>
> Additionally I would suggest a new sysvar to control the rounding
> behavior of the same temporal types, e.g.
> temporal_microsecond_rounding={round|truncate} which controls whether to
> round (as Oracle MySQL 5.6 does) or to truncate (as MariaDB does) when
> faced with fitting a larger number of decimals in a value into a smaller
> number decimals in a field. (This of course assumes that the current
> MariaDB behavior and divergence from Oracle MySQL behavior is
> intentional, and not a bug. Even if it is considered a bug it could
> probably not be changed outright at this point and the sysvar would
> still be needed.)
>
> Any thoughts on either of these? We would of course be willing to do the
> work and provide the patches for them. I just wanted to get your general
> feelings on the ideas.

New user variables are usually painful for replication.
It would be nice to avoid them.


I'd propose the following approach:

1. Rounding vs truncation:

Understand a new option in SQL_MODE:

SET sql_mode=TEMPORAL_ROUNDING;

SQL_MODE is already replicated, so no changes in the replication code 
will be needed.


2. MySQL vs MariaDB data types:

Understand some syntax like this:

CREATE TABLE t1 (a /*M!50501 MYSQL*/ TIME(6));
CREATE TABLE t1 (a /*M!50501 MARIA*/ TIME(6));

so it's possible to make a self-containing CREATE statement.

The default type on the master side should be MariaDB.

The default type of the slave side can check whether
the master is MariaDB or MySQL (I think it should be known),
and choose the corresponding data type.

> Regards,
>
> Jeremy
>
>
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