maria-developers team mailing list archive

[Aleksey Midenkov <midenok@xxxxxxxxx>]

Hi Sergei,

On Mon, Apr 5, 2021 at 8:04 PM Sergei Golubchik <serg@xxxxxxxxxxx> wrote:
>
> Hi, Aleksey!
>
> On Feb 26, Aleksey Midenkov wrote:
> > > > >
> > > > > In other words, if one can create an arbitrary history by
> > > > > manipulating @@timestamp variable,
> > > > > @@system_versioning_insert_history allows to do it more
> > > > > conveniently. But if one cannot - he cannot.
> > > >
> > > > Then do we need additional setting @@system_versioning_insert_history?
> > > > Iff one can manipulate history via @@timestamp variable let him set
> > > > row_start/row_end columns.
> > >
> > > Sure, that's possible.
> > >
> > > I just thought @@system_versioning_insert_history could be like an extra
> > > safety (not security) measure. To prevent history from being modified
> > > unintentionally.
> >
> > Well, unless one specified row_start/row_end explicitly he is safe.
> >
> > But, since we need to specify implicit system fields we cannot avoid
> > adding one more session variable. In my current iteration I made
> > @@force_fields_visible which is more straightforward in what it does:
>
> I'm sorry, I don't understand.
>
> First, visibility is pretty much unrelated concept. row_start/row_end
> can be visible or invisible, and they can be writable or not writable -
> those are orthogonal concepts.

To be able to specify them in INSERT command they must be at least
user-invisible. System-invisible fields are ignored.

>
> And second, the name is wrong, there are no "fields" row_start and
> row_end unless the user creates then explicitly. They are pieces of
> metadata that every row has, something that Oracle, for example, calls
> "pseudocolumns". Something like @@system_versioning_row_start_row_end_visible
> would be more correct, but ugly. In fact, I'd say that
> @@system_versioning_insert_history was the best one.

I think you are complicating things where complication is not needed.
Pseudo- or not they are fields. Besides, the variable is not about
system versioning. It can make any system-invisible fields visible.

>
> Regards,
> Sergei
> VP of MariaDB Server Engineering
> and security@xxxxxxxxxxx



-- 
All the best,

Aleksey Midenkov
@midenok