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Re: MDEV-339 lp:1001340 system_time_zone is wrong on Windows


Hi, Vladislav!

On Jun 14, Vladislav Vaintroub wrote:
> At file:///H:/bzr/5.5/
> revno: 3434
> revision-id: wlad@xxxxxxxxxxxxxxxx-20120614122958-bq20w9xbqjw032nk
> parent: wlad@xxxxxxxxxxxxxxxx-20120613093751-tv67fxuh1qcxm0by
> fixes bug: https://launchpad.net/bugs/1001340
> committer: Vladislav Vaintroub <wlad@xxxxxxxxxxxxxxxx>
> branch nick: 5.5
> timestamp: Thu 2012-06-14 14:29:58 +0200
> message:
>   MDEV-339, LP1001340 - system_time_zone is wrong on Windows
>   On localized Windows versions, Windows uses localized time zone
>   names.  Since characters in timezone name can be outside of ASCII
>   range,  thus not every client would be able to read variable without
>   loosing information, and even server misinterprets the encoding (it
>   does not try to interpret the encoding).
>   The fix is to use the UTC offset format "+/-hh:mm"  for
>   system_time_zone on Windows, compatible with time_zone values
>   everywhere else. UTC offset format is however  not used  if TZ
>   environment variable is defined - MySQL documents to  handle TZ
>   environment variable in OS-dependent way.

I am not sure I like this idea. UTC offset format specifies a
*different* time zone. Not the system one. Timezone that surely produces
different results for the historical dates.

Original bug report says that system_time_zone value is not a valid
MySQL (or POSIX) time zone name. But is it a problem?
When time_zone is set to SYSTEM, MariaDB will use OS functions for
date/time conversion, and not the data from timezone tables. So it will
use the system time zone *exactly*, not UTC offset approximation.
And it won't try to look up system_time_zone value in the timezone

So, I think, it's quite ok for system_time_zone to have "Westeuropäische
Sommerzeit" value. You only need to fix the charset/truncation issue and
that's all.


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