State of the MySQL support

[Richard Mortimer]

The problem with triggers in MySQL is that you quite often need elevated
privilege to set them up. That becomes a problem for an end-user program
especially when it comes time to update the database etc.

I very much thing that the more practical way is to implement a set of
statements that get wrapped in a transaction within the digikam xml/SQL
setup. I have not looked at the tags code for a while (been very busy
with other things in the past year) but thought that I had produced
enough SQL that would emulate the use of tags. From memory there is also
a database check/repair function in digikam now and it would probably be
a good idea to give that the capability of regenerating the lft and rgt
values in the tags tree.

Regards

Richard

On 11/08/2017 22:36, Mario Frank wrote:
> Yes, I saw that some time ago.
> 
> But what confuses me: There are triggers in MySQL (5.5) and also in
> MariaDB (10)
> 
> https://dev.mysql.com/doc/refman/5.5/en/trigger-syntax.html
> 
> https://mariadb.com/kb/en/mariadb/create-trigger/
> 
> I do not know since when triggers are supported in these systems. But at
> least since
> 
> the mentioned versions.
> 
> Potentially, it is now possible to switch to triggers for MySQL.
> 
> Cheers,
> 
> Mario
> 
> 
> Am 10.08.2017 um 21:23 schrieb Gilles Caulier:
>> Mario, Marcel,
>>
>> Look here :
>>
>> https://bugs.kde.org/show_bug.cgi?id=355831#c76
>>
>> Richard has posted an important patch about Mysql schema improvement.
>> Read well the comments.I tested the patch and still some
>> dysfunctions.But it's a first step...
>>
>> Gilles
>>
>> 2017-08-10 19:15 GMT+02:00 Marcel Wiesweg <marcel.wiesweg at gmx.de>:
>>> My opinion: MySQL support is important, to support network setups, to address
>>> possible performance problems and issues with parallel access inherent to
>>> sqlite.
>>> The classification of "experimental" is due to the fact that none of us
>>> (inactive me included) ever managed to make this bug-free.
>>>
>>> On the technical side, I believe most problems come from attempts to find
>>> replacement constructs for sqlite triggers. Here I would say: if there is no
>>> solution for a certain problem in MySQL, it may be solved by going away from
>>> triggers and do things in code. For example triggers on deletion, this can be
>>> solved from C++ within an transaction.
>>> The most difficult problem is the tags tree I think, here I do not have a good
>>> idea.
>>>
>>> Marcel
>>>
>>>
>>>
>>>> Hey Guys and Ladies,
>>>>
>>>> as you probably have seen the current problem with moving tags in the
>>>> hierarchy making
>>>> the DB corrupt, I would like to address this in a broader way.
>>>>
>>>> I am aware that the MySQL support is experimental (for a quite long time).
>>>> But I also experience that users complaining about problems in
>>>> combination with MySQL
>>>> becomes more frequent. The long-established devs of you may have other
>>>> experiences,
>>>> so correct me if my experience is due to my quite short time in the
>>>> digiKam world.
>>>>
>>>> As I am trying to fix the current problem, this is no overall solution
>>>> to the experimental state.
>>>>
>>>> So, what I like to address is the following:
>>>> 1) Do we have some "specialists" in MySQL in our ranks? I am no
>>>> specialist here, I am more experienced in postgres.
>>>> 2) Could we determine how many users are affected by such problems, i.e.
>>>> what is the ratio of MySQL users?
>>>> 3) What are the plans for MySQL support?
>>>> 4) Is further support for other DBMS desirable (I think of postgres)?
>>>>
>>>> Regards,
>>>> Mario
>