Leo Charre > Metadata-DB > Metadata::DB

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NAME ^

Metadata::DB

SYNOPSIS ^

   use Metadata::DB;

   my $dbh;
   my $o = new Metadata::DB($dbh);
   $o->load;
   $o->set( name => 'jack' );
   $o->set( age  =>  14 );
   $o->id(4);
   $o->save;


   my $o2 = new Metadata::DB($dbh);
   $o2->id(4);
   $o2->load;
   $o2->get( 'name' );
   $o2->set( 'age' => 44 );

Loading metadata from db

via constructor

If you pass the id to the constructor, it will attempt to load from db.

   my $o = new Metadata::DB({ DBH => $dbh, id => 'james' });
via methods

You can directly tell it what the id will be , and then request to load.

   my $o = new Metadata::DB({ DBH => $dbh });
   $o->id('james');
   $o->load;
checking for record
   my $o = new Metadata::DB({ DBH => $dbh });
   $o->id('james');
   $o->load; # you must call load
   $o->id_exists;

DESCRIPTION ^

Inherits Metadata::Base and all its methods.

new()

Argument is hash ref with at least a DBH argument, which is a database handle.

   my $o = Metadata::DB->new({ DBH = $dbh });

Optional argument is 'id'.

id()

Perl setget method. Arg is number.

id_exists()

Returns boolean. If the id is in the database, that is- if the record by this id has any entries in the metadata table, this returns true.

entries_count()

Returns number of entries for this record.

set()

Works like Metadata::Base::set()

   $o->set( name => 'Jack' );

elements()

See Metadata::Base.

add()

Works like set(), only you can provide many entries.

   $o->add(
      name => 'this',
      age => 4,
   );

write(), save()

Save to db. You call this to create a new record as well. Returns id.

load(), read()

Will attempt to load from db. YOU MUST CALL load() to check what is in the database. If load is not called or triggered, the data in the object is just the data in the object. Instead of a representation of what is or may be stored.

loaded()

Returns boolean If load() was triggered or called or not.

lookup()

Takes no argument. Returns record id. On fail returns undef, reason for failure is in errstr().

This is another kind of load() method. (Internally it's also a kind of very specific search.) It requires that first you have some attribute set() in the instance. It will look up the records by those attributes, if one and one only matches those attributes exactly, then the record's id() is automatically set and load() is called.

For example, if you have a "person" record. That you know contains an attribute called "last_name" with value "Jefferson"- If there is only one record matching that, you can load the metadata record via the last name.

   my $m = Metadata::DB->new({ DBH => $dbh });
   $m->set( last_name => 'Jefferson' ); # has not yet been loaded
   $m->lookup or print ("was not found because :".$m->errstr ) and exit;

   # now you can access all the record's metadata which has been loaded..
   my $record_id = $m->id;
   my $last_name = $m->get('last_name');
   my $first_name = $m->get('first_name');
   # etc..

Note that if you had had two records with last name 'Jefferson', lookup() would fail, and errstr() would contain a message saying that too many records matched.

get_all()

Returns hashref with all meta. This only returns what is stored in the object. Thus..

   my $m = Metadata::DB->new({ DBH => $dbh });
   $m->id( 3 );
   $m->set( name => 'billy');

   $m->get_all; # returns { name => 'billy' }

If you want to get everything that may be in the database, call load() or lookup().

get()

See Metadata::Base.

   $o->get('name');

CAVEATS ^

WARNING Calling save() before load() will delete all record metadata previously saved.

Delete ALL metadata with id 5 and save only 'name marc'.

   my $m = Metadata::DB->new({ DBH => $dbh, id => 5 });
   $m->set( name=> 'marc' );
   $m->save;

After, this will NOT load the metadata 'name marc':

   my $m = Metadata::DB->new({ DBH => $dbh, id => 5 });
   $m->get( 'name' );

This example WILL load the metadata:

   my $m3= Metadata::DB->new({ DBH => $dbh, id => 5 });
   $m->load;
   $m->get( 'name' );

This example will NOT delete metadata and will add instead:

   my $m = Metadata::DB->new({ DBH => $dbh, id => 5 });
   $m->load;
   $m->set( age => 25 );
   $m->save;

Why? Why not just override get and get all to take care of this? Wny not just call load() automatically?? Because that's up to you. You MAY want to NOT do this cpu intensive operation. Maybe you want to insert a million entries really quickly, thus you dont want to load every time, maybe you already know there is nothing in there.

SEE ALSO ^

Metadata::Base Metadata::DB::Base Metadata::DB::Indexer Metadata::DB::Analizer Metadata::DB::WUI

BUGS ^

Please contact the AUTHOR for any issues, suggestions, bugs etc.

AUTHOR ^

Leo Charre leocharre at cpan dot org

COPYRIGHT ^

Copyright (c) Leo Charre. All rights reserved.

LICENSE ^

This program is free software; you can redistribute it and/or modify it under the same terms and conditions as Perl itself.

This means that you can, at your option, redistribute it and/or modify it under either the terms the GNU Public License (GPL) version 1 or later, or under the Perl Artistic License.

See http://dev.perl.org/licenses/

DISCLAIMER ^

THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.

Use of this software in any way or in any form, source or binary, is not allowed in any country which prohibits disclaimers of any implied warranties of merchantability or fitness for a particular purpose or any disclaimers of a similar nature.

IN NO EVENT SHALL I BE LIABLE TO ANY PARTY FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION (INCLUDING, BUT NOT LIMITED TO, LOST PROFITS) EVEN IF I HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE

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