[odb-users] schema validation

[Alexander A. Prokhorov]

Thanks!

On 26.10.2012 17:02, Boris Kolpackov wrote:
> Hi Alexander,
>
> Alexander A. Prokhorov <alexander.prokhorov at datadvance.net> writes:
>
>> Application is quite agile, schema often experiences minor changes, and
>> it's very desirable to perform a meaningful schema check every time I
>> open a new SQLite file.
>>
>> Otherwise, as I understand, user may encounter some database-related
>> exceptions/errors in runtime, which is highly undesirable.
>>
>> So, the question is, is there any recommended way to match current
>> schema (in odb::schema_catalog, I suppose) to be subset of schema in
>> some database?
> There is no automatic database schema versioning in ODB yet (we may
> add something like this in the future as part of the schema evolution
> work).
>
> In the meantime, it should be quite easy to implement this by storing
> the version of the schema in the database itself (this also seems to
> be the recommended way to do schema versioning). You could even create
> a small persistent class to assist with this, something along these
> lines:
>
> #pragma db object
> struct schema_version
> {
>    schema_version () {}
>    schema_version (unsigned short mj, unsigned short mn)
>      : id (1), major (mj), minor (mn)
>
>    #pragma db id
>    unsigned short id;
>
>    unsigned short major;
>    unsigned short minor
> };
>
> Then when creating a new database, you would also store the version:
>
> schema_version sv (2, 3);
> db.persis (sv);
>
> And when opening an existing database, you would check the version:
>
> schema_version sv;
> db.load (1, sv);
>
> if (sv.major < 2)
> {
>    // Incompatible schema version.
> }
>
> Boris


-- 
Alexander A. Prokhorov
Head of Software Development
DATADVANCE
Mob. +7 903 6249039
alexander.prokhorov at datadvance.net
prokher at datadvance.net

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