Multi-user operation (was Re: Query for splits)

[Phil Longstaff]

On Wed, 2006-15-11 at 13:33 -0500, Derek Atkins wrote:
> Yes.  Keep in mind that once you get to the point of getting told
> "object is locked", it's already too late..  There's no error code
> returned from begin_edit() that could get displayed to the user.  In
> this case I think it's "last writer wins", but I think that's okay.
> You could make begin_edit() block until the other client commits the
> edit on the same object, but that might impose some usability issues.
> 
> As for the refresh, yes, you could refresh on begin_edit, but you
> really should refresh more often than that.  The current PG Backend
> uses NOTIFY() and events to inform multiple clients that changes have
> been made.  This isn't portable, so we can't use this method directly.
> BUT we should periodically poll the database and ask something like:
> 
>   select * from Changes where change_time > [last_poll]

I guess what I'm proposing/raising is the idea of another qof API which
would tell the backend that I want to work on/edit an existing object.
This would try to lock the object and return a boolean indicating
success.  GC would call this API for an object when the edit dialog box
was first opened.

This would handle trying to edit an object but would not handle new
objects i.e. someone else creates a new account.  It's unfortunate that
there is not a general NOTIFY mechanism which would handle this.  Of
course, another way to handle the general issue is a GC server.

Phil