[sprog-users] Re: DBI Gear

[Matthew K. <df...@ya...>]

>Obviously Sprog needs the ability to source data from
a database via
> DBI. 

I'm trying to write one at the moment.  

>The tricky part of writing data source gears is the
need for
> non-blocking IO.  If someone submits a query that
takes several minutes
> to complete, then we obviously want the "Stop"
button to be functional
> during that time.
 
> Does anyone know if there are any hooks in DBI for
using it
> asynchronously?

I'm not aware of anything built into DBI directly, but
if the application needs to remain responsive while
the query's executing then I would think that threads
would be the best way to go.  This is a bit more
elegant than using fork(), particularly on platforms
where Perl's support for fork is a bit of a kludge (I
know it doesn't currently run on Windows, but I guess
there shouldn't be anything that precludes it).  The
only drawback is that it makes this gear dependent on
having Perl 5.8 installed.

Anyway, I've got it about 50% written, when I'm close
to finished I wouldn't mind getting some feedback or
suggestions about it.

One unrelated question:  I haven't yet figured out how
you're meant to modify a machine once you've
constructed it (ie add or remove gears).  The gears
seem to connect OK when you drag them from the list on
the left, but I haven't yet found a way of
reconnecting gears which become disconnected in the
machine (due to deleting gears), or to connect new
gears in the middle of an existing machine.  Is there
something I'm missing ?


	

	
		
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