in reply to Re: dbi_query_iterator and my misunderstanding the $row
in thread dbi_query_iterator and my misunderstanding the $row

Thanks! But why return $oldrow->[0] instead of just $row->[0]? 

        my $oldrow = $row;
        $row = $sth->fetchrow_arrayref;
        return $oldrow->[0];

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Re^3: dbi_query_iterator and my misunderstanding the $row
by japhy (Canon) on Mar 02, 2007 at 13:43 UTC
    Oh, sorry. Maybe I misunderstood. Does the code actually work, and you want to know why it works?

    $oldrow is the previous row. The function that builds the iterator stores the first row before it creates the iterator function: 

    sub dbi_query_iterator {
  my ($sth, @params) = @_;

  $sth->execute(@params) or return;

  # get the first row of results NOW
  my $row = $sth->fetchrow_arrayref();

  return Iterator {
    my $action = shift() || 'nextval';

    if ($action eq 'exhausted?') {
      return ! defined $row;
    } elsif ($action eq 'nextval') {

      # save the current row of results
      my $oldrow = $row;

      # get the next row of results
      $row = $sth->fetchrow_arrayref;

      # return the previous row (before we advanced)
      return $oldrow->[0];
    }
  }
}

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