interface ideas for non-blocking mode

[david nicol]

In the recent roadmap announcement, Tim Bunce wrote:

> =head2 Other Enhancements
> 
> * Support non-blocking mode for drivers that can enable it in their
>  client API.


I have just startedworking with DBI but I'm doing something that would
benefit from a non-blocking mode.


I would like a $sth->ready() function, which would start false but
become true (or throw errors when RaiseError is set) when there is
at least one whole row available to fetch, and a $sth->done() function
to indicate that there is nothing left to fetch.  The fetchrow and
fetchall functions would provide as much data as has been made available
so far -- fetchrow would return immediately when there is
less than a row in the input buffer, fetchall would return all
the whole rows that have come in so far.

   $h->more would be !$h->done

So we'd have this:

  sub CheeseLister(){

        $dbh = $DBI->connect($DSN,$username,$password,
           {RaiseError=>1,NonBlocking=>1});

        $sth = $dbh->prepare('SELECT cheese FROM BigTable');

        1 while !$sth->ready; # in case prepare returned early

        $sth->execute(); # returns as soon as possible

        print "Here are the cheeses:\n";
        my $continuation;
        $continuation =
              sub {
                    $sth->ready or return undef;
                    print @{$_},"\n"
                       foreach ( @{$sth->fetchall_arrayref});
                    $sth->more; # true or false -- is there more?
              }
   }

   ...

   $CheeseEngine = Cheeselister;
   while($CheeseEngine()){
      ... # do something else while we wait
   }
   
   print "\nThat's all folks!\n";


Does that match other people's thoughts on what nonblocking mode
should look like?

David Nicol