Re: DBD::XML

On 19/8/16 11:51, Tim Bunce wrote:
> 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?

Nope, that's me creating random test data to poke around.
>
>> use DBD::XML;
> (Ideally users shouldn't need to use the driver module explicitly.)

I'm assuming after registration that would go away, or am I wrong?
>
>> 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'?

"Pinched from" to get a bootstrap while I'm developing before registration.
>
>> 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.)
Thanks for the pointer - that's useful to know.
>
> Are any other XML Schema supported, or supportable?
I hope so, once I'm ready to create more test data beyond the trivial 
stuff I'm using to get started.
>
> 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?
I'm hoping to do chunk by chunk, but that's not done yet.
> In other words, can it read files larger than the available memory?
> (Not related to the naming, just curious :)
I really hope so, but not yet.  I need to walk before I can run :-)

-Nigel
>
> Tim.