[vtk-developers] vtkSQLDatabase

[Jeff Baumes]

> 4. Adding a uniform interface for creating and dropping databases
>    and tables?

Is the goal here to create database-independent schemas, or to store
database schemas in a way that is easy to reference later on (perhaps
to recreate the same schema at different times, populate GUI drop-down
menus, or perform some type of analysis / visualization of the
database)?

If it is the first, this will probably not happen often due to the
database-dependent features that you mention.  Unless the
"implementation-specific stuff" fields that you describe are empty, it
will not work across database types.

I can see the second as very useful.  It would be even more useful if
a database schema structure could be automatically populated given a
database URL.  In MySQL you could possibly parse a "SHOW CREATE TABLE"
query to do this.

I would suggest also adding some way to specify foreign keys, as they
are often important in understanding the connections between tables.

Jeff

> Tim Shead wrote:
> > I'd argue that SetURL()/GetURL() don't make much sense on a concrete
> > database instance, and you don't really need them since your
> > CreateFromURL() factory method can dispatch the correct parameters to
> > the correct concrete database type.
>
> I agree that SetURL shouldn't be public, but it can be useful to keep
> the URL of the database around... if a reconnect is required or if you
> want to present information about the database to the user, it could be
> handy. How about a protected SetURL() method used by CreateFromURL()?
>
> That would change the usage from the current classes, where an
> implementation-specific instance is created and then its filename, URL,
> etc. are set. Are there any cases not handled by CreateFromURL() that
> are accommodated by the current code?
>
>         David
>
> >
> > > -----Original Message-----
> > > From: vtk-developers-bounces+tshead=sandia.gov at vtk.org
> > > [mailto:vtk-developers-bounces+tshead=sandia.gov at vtk.org] On
> > > Behalf Of David C Thompson
> > > Sent: Tuesday, November 27, 2007 5:23 PM
> > > To: Wilson, Andrew T; VTK Developer List
> > > Subject: [vtk-developers] vtkSQLDatabase
> > >
> > > Andy (et al.),
> > >
> > > We're mulling over the use of vtkSQLDatabase for a project
> > > but it would require a few additions to the existing class.
> > > Do you (or anyone) have objections to
> > >
> > > 1. Adding a URL parser to the vtkSQLDatabase class?
> > >
> > >    This way, sqlite, mysql, and postgres could share a common
> > >    SetURL() method instead of the current SetFileName,
> > >    Set{HostName,UserName,Password,Port}, SetURL trichotomy.
> > >    A vtksys::RegularExpression would match
> > >
> > >      file:///path     or maybe     sqlite:///path       - for SQLITE
> > >      mysql://[user[:password]@]hostname[:port]/database - for MySQL
> > >      pgsql://[user[:password]@]hostname[:port]/database - for Postgres
> > >
> > >    It seems easily extensible to other backends and could
> > > conceivably be
> > >    used to have vtkSQLDatabase create the proper subclass
> > > given the url.
> > >    There would be a static method to examine a character string and
> > >    return username, password, hostname, port, and database(or file
> > >    path) as appropriate, with NULLs returned for portions not present:
> > >
> > >    static void ParseURL( const char* URL, char*& protocol,
> > >       char*& user, char*& passwd, char*& host, char*& port,
> > >       char*& path );
> > >    static vtkSQLDatabase* CreateFromURL( const char* URL );
> > >    vtkSetStringMacro(URL);
> > >    vtkGetStringMacro(URL);
> > > ...
>
>
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-- 
Jeff Baumes, Ph.D.
R&D Engineer, Kitware Inc.
(518) 371-3971 x132
jeff.baumes at kitware.com