Martijn Tonies wrote:

>Well, for example, Database Workbench uses this ability to alter
>several things at once for a table in the GUI.
>
>You can, for example, add a couple of columns, drop a few,
>modify and add some triggers. Next press "Save" and all actions
>get saved or backed out when something critical happens. This
>"critical" part can be a typo in a trigger, for example.
>
>How would this work with Vulcan? My guess is, that it doesn't -
>right?
>
>

I agree with the need for the capability. But there's a much better way
to provide it. An "upgrade table" verb that transforms an existing
table into new state is a great deal more powerful than a sequence of
uncommitted alters and is safer to boot. It also addresses the
restartability problem of upgrade scripts since an "upgrade" to the
table's current state is a no-op.

The "upgrade table" statement isn't on my plate, but is straightforward
to implement. Syntactically, it's equivalent to "create table". The
rest of the implementation is looping through the syntax nodes checking
the new definition against the existing one. If a difference is found,
a change to the metadata tables is done then and there. To really
exploit it for development, however, you need a library function to
generate "upgrade table" statement directly from the database, then wrap
a GUI around it.

--

Jim Starkey
Netfrastructure, Inc.
978 526-1376