[odb-users] std::map key as part of primary key

[Alessandro Bellina]

Thank you Boris, I think vector may do the trick.

Alessandro


On Wed, Aug 21, 2013 at 6:33 AM, Boris Kolpackov <boris at codesynthesis.com>wrote:

> Hi Alessandro,
>
> Alessandro Bellina <abellina at gmail.com> writes:
>
> > #pragma db object
> > struct Test
> > {
> > ...
> > std::map<std::string, int> my_values;
> > #pragma db id
> > unsigned long id;
> > };
> >
> > First, I insert an item in Test, and that works as expected. But an
> update
> > deletes everything for that foreign key and then reinserts. I thought it
> > would match on the foreign key (Test::id), then the std::map key, and
> > update that row.
>
> The problem is, std::map doesn't store any information about whether
> this is a new row, an updated row, or an unchanged row. In other words,
> it  doesn't keep any change information.
>
> In ODB, we address this with special change-tracking containers. See
> Section 5.4, "Change-Tracking Containers" for more information. While
> there is no change-tracking equivalent for std::map yet, it is definitely
> possible to implement one and we will probably do it in near future.
> There is an std::vector equivalent which you maybe can use in the
> meantime.
>
> Boris
>