Re: sth->prepare() setting Active?

On Thu, Sep 29, 2016 at 11:30:08PM -0000, Greg Sabino Mullane wrote:
> 
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: RIPEMD160
> 
> 
> > Should a call to prepare() return an Active statement? (i.e. $sth->{Active} == 1)
> >
> > This appears to be the behaviour of DBD::Sybase, but not DBD::Pg
> 
> I don't think there is a canonical answer to that, but I can say that 
> DBD::Pg in most cases will not even talk to the server until the first 
> execute() after the prepare(), so it not being Active seems a sane 
> interpretation.


> The docs for DBD::Pg:
> 
>    Indicates if a handle is active or not. For database handles, this 
>    indicates if the database has been disconnected or not. For statement 
>    handles, it indicates if all the data has been fetched yet or not. 
>    Use of this attribute is not encouraged.
> 
> As far as I can tell, DBD::Sybase makes not effort to do anything special 
> regarding that attribute.

DBD::Sybase has this

    /* Re-enable the active flag here (in 1.05_03) to fix bug with
       finish not getting called correctly */
    DBIc_ACTIVE_on(imp_sth);

at the end of syb_st_prepare() in dbdimp.c

So, it explictly sets Active to deal with some issue that I haven't
fully delved into.

> In short, I would not rely upon it, especially across DBDs.

That's unfortunate, because Class::DBI does.

$ grep -r Active .
./lib/Class/DBI.pm:		$sth->execute(@$args) unless $sth->{Active};

(from sth_to_objects)

As far as I can see, this is to work out whether the sth that's been
passed in has already had execute called on it (e.g. part of a multiple
result loop). Removing the $sth->{Active} check (and ensuring Ima::DBI
always calls prepare and not prepare_cached (I haven't figured out what's
going on there yet) gets Class::DBI working with DBD::Sybase.

Our current code overrides db_Main which seems like an unnecessary hack
to me, and confuses Class::DBI somewhat, triggering warnings.

I'm halfway down this rabbit hole and not really sure which turning to
take now!

-- 
Russell Howe
[email protected]