DBD::Proxy - fix rows() for fetch()

[Philip Dye]

Here is the patch implementing 'rows fetched so far'.  rows() now also 
properly returns -1 when the $sth->{'proxy_rows'} is not defined.  It is 
debatable whether execute should undefine proxy _rows or set it to 0.  
Unless someone has a good argument otherwise, it seems to me that 
undefining proxy_rows is the most reasonable thing to do there.

- philip
Philip Dye wrote:
Tim,

You are quite correct.  I was too hasty in writing that first patch.  
According to the DBI documentation there are actually two approaches 
in vogue for select operations:

    rows <http://search.cpan.org/%7Etimb/DBI/DBI.pm#___top>

    $rv = $sth->rows;

    Returns the number of rows affected by the last row affecting
    command, or -1 if the number of rows is not known or not available.

    Generally, you can only rely on a row count after a /non/-|SELECT|
    |execute| (for some specific operations like |UPDATE| and
    |DELETE|), or after fetching all the rows of a |SELECT| statement.

    For |SELECT| statements, it is generally not possible to know how
    many rows will be returned except by fetching them all. Some
    drivers will return the number of rows the application has fetched
    so far, but others may return -1 until all rows have been fetched.
    So use of the |rows| method or |$DBI::rows| with |SELECT|
    statements is not recommended.

I will implement the 'rows fetched so far' model.  Oddly enough 
neither my earlier fix or this fix will fix the problem I had with 
Rose::DB::Object::load() that expects sth->rows() to be greater than 
zero if and only if the most recent fetch() has returned a row.  I 
posted a fix Rose::DB::Object::load() to its mailing list.

Ideally, the implementation of sth->rows() would become standardized 
so that its value would be dependable one way or the other after a 
fetch().

Respectfully,
Philip Dye
Senior Research Systems Programmer
Computing Facilities Group
School of Computer Science
[EMAIL PROTECTED]

*** DBD/Proxy.pm        Fri Aug 17 07:54:55 2007
--- DBD/Proxy.pm.new    Fri Aug 17 07:55:06 2007
*************** sub execute ($@) {
*** 510,515 ****
--- 510,516 ----
  
      # new execute, so delete any cached rows from previous execute
      undef $sth->{'proxy_data'};
+     undef $sth->{'proxy_rows'};
  
      my $rsth = $sth->{proxy_sth};
      my $dbh = $sth->FETCH('Database');
*************** sub fetch ($) {
*** 590,595 ****
--- 591,599 ----
  
      my $data = $sth->{'proxy_data'};
  
+     defined($sth->{'proxy_rows'}) ||
+       ( $sth->{'proxy_rows'} = 0 );
+ 
      if(!$data || [EMAIL PROTECTED]) {
        return undef unless $sth->SUPER::FETCH('Active');
  
*************** sub fetch ($) {
*** 613,625 ****
      my $row = shift @$data;
  
      $sth->SUPER::STORE(Active => 0) if ( $sth->{proxy_cache_only} and [EMAIL 
PROTECTED] );
      return $sth->_set_fbav($row);
  }
  *fetchrow_arrayref = \&fetch;
  
  sub rows ($) {
      my($sth) = @_;
!     $sth->{'proxy_rows'};
  }
  
  sub finish ($) {
--- 617,630 ----
      my $row = shift @$data;
  
      $sth->SUPER::STORE(Active => 0) if ( $sth->{proxy_cache_only} and [EMAIL 
PROTECTED] );
+     $sth->{'proxy_rows'}++;
      return $sth->_set_fbav($row);
  }
  *fetchrow_arrayref = \&fetch;
  
  sub rows ($) {
      my($sth) = @_;
!     $sth->{'proxy_rows'} || -1;
  }
  
  sub finish ($) {