Re: DBD::XML

On Fri, Aug 19, 2016 at 10:09:45AM -0400, Nigel Horne wrote:
> On 8/19/16 9:56 AM, Tim Bunce wrote:
> > On Fri, Aug 19, 2016 at 09:30:32AM -0400, Nigel Horne wrote:
> > > 
> > > Apart from one change I need to make in terms of column names, I'm pretty
> > > much ready to start working on a 0.01 CPAN release.  It's read-only, but
> > > that's all I need.  How do I set about requesting driver registration, or is
> > > this mentioning enough?
> > Probably :)
> > 
> > But I wonder about the name. "DBD::XML" seems to be a bold name,
> > implying that it's _the_ DBI interface for data stored in XML files.
> > Of course the same kind of issue applies to many other drivers,
> > so it's not a major concern, but does seem worth dicussing.
> 
> I'm more than happy to entertain other names if you have any suggestions.

I've some random questions and observations below...

> So, here's the example I've started with to get the code basic interface
> going and tested.  The code I have works with this trivial example.
> 
> data/person.xml:
> 
> <?xml version="1.0" encoding="US-ASCII"?>
> <table>
>     <row id="1">
>         <name>Nigel Horne</name>
>         <email>[email protected]</email>
>     </row>
>     <row id="2">
>         <name>A N Other</name>
>         <email>[email protected]</email>
>     </row>
> </table>

Does that format ('table', 'row', 'id') correspond with a known XML Schema?

> use DBD::XML;

(Ideally users shouldn't need to use the driver module explicitly.)

> my $dbh = DBI->connect('dbi:XML(RaiseError => 1):');
> $dbh->func('person', 'XML', "$Bin/../data/person.xml", 'ad_import');  # to be replaced with xml_import once the driver has been registered

I presume ad_import comes from DBD::AnyData. Is that 'inspired by',
or 'is a fork of', or 'using under the hood'?

> my $sth = $dbh->prepare("SELECT * FROM person");
> $sth->execute();
> 
> while (my $href = $sth->fetchrow_hashref()) {
>     my $d = Data::Dumper->new([$href]);
>     print "got data:\n", $d->Dump();
> }

($sth->dump_results can be handy for little example scripts.)

Are any other XML Schema supported, or supportable?

Is the XML and/or the parsed data loaded into memory or does each
$sth->fetch call pull the next chunk from the XML parser?
In other words, can it read files larger than the available memory?
(Not related to the naming, just curious :)

Tim.