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lib/DBIx/SystemCatalog.pm  view on Meta::CPAN

	$dbh->disconnect;

=head1 DESCRIPTION

This module can access to system catalog of database through DBI(3) interface.
Basic methods access to objects through standard DBI(3) interface 
(call C<tables()> for list of objects and C<selectall_arrayref()> with basic
SQL to get structure of objects).

Constructor looks for specific module implemented database interface for
used DBD driver (obtained from DBI(3)). These module can add faster and better
functions such as relationships or types of objects.

=head1 CONSTANTS

=head2 Type of object

=over 4

=item SC_TYPE_UNKNOWN

=cut

sub SC_TYPE_UNKNOWN () { return 0; }

=item SC_TYPE_TABLE

=cut

sub SC_TYPE_TABLE () { return 1; }

=item SC_TYPE_VIEW

=back

=cut

sub SC_TYPE_VIEW () { return 2; }

=head1 THE DBIx::SystemCatalog CLASS

=head2 new (DBI)

Constructor create instance of this class and bind DBI(3) connection.
Then obtain used driver name from DBI(3) class and look for descendant
of this class for this driver (e.g. C<DBIx::SystemCatalog::Oracle> module
for C<Oracle> driver). If success, return instance of this more specific class,
otherwise return itself.

You must passed connected DBI(3) instance as first argument to constructor
and you can't disconnect that instance while you use this instance of
DBIx::SystemCatalog.

	$catalog = new DBIx::SystemCatalog $dbh

=cut

sub new {
	my $class = shift;
	my $dbi = shift;
	my $obj = bless { dbi => $dbi, class => $class, schema => '' },$class;
	$obj->{Driver} = $obj->{dbi}->{Driver}->{Name};

	# Only base class can dispatch to more specific class
	if ($class eq 'DBIx::SystemCatalog') {
		my $driver_name = 'DBIx::SystemCatalog::'.$obj->{Driver};
		eval "package DBIx::SystemCatalog::_safe; require $driver_name";
		unless ($@) {	# found specific driver
			$driver_name->import();
			return $driver_name->new($dbi,@_);
		}
	}

	# Hmm, we are specific class or specific class not found
	return undef unless $obj->init(@_);
	return $obj;
}

=head2 init

Because C<new()> is quite complicated, descendant inherits this C<new()>
constructor and redefine C<init()> constructor which is called from C<new()>.

C<init()> gets all arguments from C<new()> with one exception - instead of
name of class this constructor get instance of object.

Constructor must return true value to make successful of creating instance
of object. In this base class is C<init()> abstract, always true.

This method isn't called directly from user.

=cut

sub init { 1; }

=head2 schemas

Method must return list of schemas from database. In this base class method
always return empty list, because standard DBI(3) method can't get list of
schemas.

	my @schemas = $catalog->schemas()

=cut

sub schemas {
	return ();
}

=head2 schema (NAME)

Method set current schema name. Other methods work only with this schema.
Because working with one schema is typical work, all methods in specific
class need this schema name. Method can set schema (descendant need not 
redefine it).

	$catalog->schema('IS')

=cut

sub schema {