maria-developers team mailing list archive

[Alexander Barkov <bar@xxxxxxxxxxx>]

Hi Sergei,


I'm not sure what to do with this:

> MariaDB [test]> select
>     -> timediff('2014-01-01 00:00:00' , '2014-01-01 01:00:00' ),
>     ->     timediff(20140101000000.000 , 20140101010000.000  ),
>     -> timediff(20140101000000.000 , '2014-01-01 01:00:00' ),
>     -> datediff('2014-01-01 00:00:00' , '2014-01-02 01:00:00' ),
>     ->     datediff(20140101000000.000 , 20140102010000.000  ),
>     -> datediff(20140101000000.000 , '2014-01-02 01:00:00' )\G
> *************************** 1. row ***************************
> timediff('2014-01-01 00:00:00' , '2014-01-01 01:00:00' ): -01:00:00
>      timediff(20140101000000.000 , 20140101010000.000  ): -01:00:00.000
>    timediff(20140101000000.000 , '2014-01-01 01:00:00' ): NULL
> datediff('2014-01-01 00:00:00' , '2014-01-02 01:00:00' ): -1
>      datediff(20140101000000.000 , 20140102010000.000  ): -1
>    datediff(20140101000000.000 , '2014-01-02 01:00:00' ): -1
> 1 row in set (0.03 sec)

Notice, it returns NULL in one case.

The problem is in this piece of the code:

>   if (args[0]->get_time(&l_time1) ||
>       args[1]->get_time(&l_time2) ||
>       l_time1.time_type != l_time2.time_type)
>     return (null_value= 1);

get_time() forces decimal-to-time conversion to truncate the date part
and return MYSQL_TIMESTAMP_TIME.

get_time() does not force string-to-time conversion to truncate the date 
part. It still returns the full MYSQL_TIMESTAMP_DATETIME.

I'm afraid a lot of the code rely in this behavior.
If we fix string-to-time conversion, mtr will start to fail in other cases.

Any ideas what to do?