Re: Help sought with definition and implementation of ParamTypes attribute

On Mon, Oct 13, 2008 at 08:38:08AM +0200, H.Merijn Brand wrote:
> On Sun, 12 Oct 2008 21:25:12 +0100, Tim Bunce <[email protected]>
> wrote:
> > On Sun, Oct 12, 2008 at 02:55:51AM -0000, Greg Sabino Mullane wrote:
> > > 
> > > > values are hashrefs of type information in the same form as that
> > > > provided to the various bind_param() methods
> > > ...
> > > 
> > > > I'm not sure why the values of the keys are hash references unless
> > > > multiple values are to be stored. If multiple values per key are stored
> > > > what are they typically? I can only find one DBD which implements
> > > > ParamTypes (DBD::Pg) and unless I am mistaken it sets the values of the
> > > > keys to a scalar value - the type of the parameter.
> > > 
> > > Yes, it's scalar values in DBD::Pg. If I recall correctly, it was done that
> > > way simply because it seemed better to return a simple name. To be 100%
> > > accurate it should probably return a hashref because that's what bind_param
> > > takes. In other words:
> > > 
> > >   $sth->bind_param('$1', 234, { pg_type => SQL_INTEGER });
> > >   warn Dumper $sth->{ParamTypes};
> > > 
> > > gives:
> > > 
> > > $VAR1 = {
> > >           '1' => 'integer'
> > >         };
> > > 
> > > When it should technically return:
> > > 
> > > $VAR1 = {
> > >           '1' => { pg_type => 'SQL_INTEGER' }
> > >         };
> > 
> > The intention is that this code:
> > 
> >     $ParamTypes  = $sth1->{ParamTypes};
> >     $ParamValues = $sth1->{ParamValues};
> > 
> >     $sth2->bind_param( $_, $ParamValues->{$_}, $ParamTypes->{$_} )
> >         for keys %$ParamTypes;
> > 
> > should make the values bound to $sth2, and the way they're treated by
> > the driver, be the same way as they were for $sth1.
> > 
> > So { '1' => 'integer' } sure looks like a bug.
> 
> But the underlying question was if it should return
> 
>   $VAR = { 1 => 1 };
> 
> or
> 
>   $VAR = { 1 => { pg_type => 1 }};
> 
> My DBD::Unify currently does the first. It returns numerical scalars,
> not hash-refs

I've no problem with ParamTypes returning the same value that was passed
to bind_param(), and bind_param() allows an integer:

    $sth->bind_param( $i, $value, 1 );

is defined to be a shorthand for

    $sth->bind_param( $i, $value, { TYPE => 1 } ); # and TYPE 1 is SQL_CHAR

It's important to remember, though, that that integer is the ANSI/ISO
defined TYPE value, not some driver-specific value.

Tim.


> > > However, bind_param currently saves the value to an internal form, without
> > > saving how it got there, which makes the key of that inner hash ('pg_type')
> > > difficult to show. Because the value, SQL_INTEGER, is really a constant, it's
> > > equally difficult to know to output 'SQL_INTEGER' - we'd really have to output
> > > the number it maps to.
> > 
> > Yes. Outputting the _string_ "SQL_INTEGER" would be wrong as it wouldn't
> > work for the code above.
> > 
> > > I can easily adjust ParamTypes in DBD::Pg to give a hashref, if that's
> > > what you end up doing for DBD::ODBC
> 
> -- 
> H.Merijn Brand          Amsterdam Perl Mongers  http://amsterdam.pm.org/
> using & porting perl 5.6.2, 5.8.x, 5.10.x, 5.11.x on HP-UX 10.20, 11.00,
> 11.11, 11.23, and 11.31, SuSE 10.1, 10.2, and 10.3, AIX 5.2, and Cygwin.
> http://mirrors.develooper.com/hpux/           http://www.test-smoke.org/
> http://qa.perl.org      http://www.goldmark.org/jeff/stupid-disclaimers/