Re: Is DBD::ODBC breaking the rules with this optimisation?

Great. Thanks Martin.

Tim.

On Tue, Dec 14, 2010 at 03:26:41PM +0000, Martin J. Evans wrote:
> On 13/12/10 21:00, Tim Bunce wrote:
> > On Mon, Dec 13, 2010 at 05:30:10PM +0000, Martin J. Evans wrote:
> >> See RT http://rt.cpan.org/Public/Bug/Display.html?id=63550 which started this off.
> >>
> >> DBD::ODBC optimises calls to the do method when no parameters are
> >> involved. Normally do is just a shortcut for prepare/execute except it
> >> should only be for non-result-set generating statements and hence does
> >> not return a statement handle. ODBC can optimise the do method to
> >> simply call SQLExecDirect instead of the normal SQLPrepare/SQLExecute
> >> (one round trip and other advantages). DBD::ODBC has been this way for
> >> years.
> >>
> >> However, the person reporting this issue is attempting to use the
> >> handle passed to an error handler when do fails to obtain the
> >> Statement attribute. The handle DBD::ODBC passes in to the error
> >> handler is the connection handle as DBD::ODBC never created a DBI
> >> statement handle and hence there is no Statement attribute to access.
> > 
> > Actually, the database handle _does_ have a Statement attribute
> > http://search.cpan.org/~timb/DBI-1.615/DBI.pm#Statement
> 
> so it does, I missed that.
> 
> > Feel free to patch the docs to change "most recent prepare method"
> > to "most recent prepare() or do() method".
> 
> done
>  
> >> Is DBD::ODBC breaking the rules here with this optimisation?
> > 
> > No.
> 
> excellent, so it is just failing to call STORE for the Statement in the optimised do method - which I have just fixed.
>   
> > The DBI docs for do() should have a note along the lines that
> > "Drivers are free to avoid the overhead of creating an DBI statement
> > handle for do(), especially if there are no parameters. In which case
> > error handlers, if invoked during do(), will be passed the database handle."
> 
> done
>  
> > The docs for drivers using this approach should note the fact that a
> > statement handle isn't created, and that error handlers like HandleErr
> > will be called with the $dbh.
> 
> done
> 
> > Tim.
> 
> Thanks Tim.
> 
> BTW, I owe you an email as discussed at LPW - will try to get to it today.
> 
> Martin
> -- 
> Martin J. Evans
> Easysoft Limited
> http://www.easysoft.com
>