Re: Help sought with definition and implementation of ParamTypes attribute

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:
> > 
> > -----BEGIN PGP SIGNED MESSAGE-----
> > Hash: RIPEMD160
> > 
> > 
> > > 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

> > 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

-- 
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