maria-developers team mailing list archive

[Igor Babaev <igor@xxxxxxxxxxxx>]

On 07/13/2011 02:34 PM, Timour Katchaounov wrote:
> Igor,
> 
> Could you please review this fix for bug lp:809266.

Timour,

If you have full coverage of the new code from the patch
then you may push it.

Regards,
Igor.


> 
> Timour
> 
> ------------------------------------------------------------
> revno: 3104
> revision-id: timour@xxxxxxxxxxxx-20110713211507-j9v80yk2tzae8tq2
> parent: timour@xxxxxxxxxxxx-20110713141146-339e3xwz17hogqsb
> fixes bug(s): https://launchpad.net/bugs/809266
> committer: timour@xxxxxxxxxxxx
> branch nick: 5.3-mwl89
> timestamp: Thu 2011-07-14 00:15:07 +0300
> message:
>   Fix bug lp:809266
> 
>   Analysis:
>   This is a bug in MWL#68, where it was incorrectly assumed
>   that if there is a match in the only non-null key, then
>   if there is a covering NULL row on all remaining NULL-able
>   columns there is a partial match. However, this is not the case,
>   because even if there is such a null-only sub-row, it is not
>   guaranteed to be part of the matched sub-row. The matched sub-row
>   and the NULL-only sub-row may be parts of different rows.
> 
>   In fact there are two cases:
>   - there is a complete row with only NULL values, and
>   - all nullable columns contain only NULL values.
> 
>   These two cases were incorrectly mixed up in the class member
>     subselect_partial_match_engine::covering_null_row_width.
> 
> 
>   Solution:
>   The solution is to:
>   - split covering_null_row_width into two members:
>     has_covering_null_row, and has_covering_null_columns, and
>   - take into account each state during initialization and
>     execution.