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package DBIx::Class::Storage;
use strict;
use warnings;
use base qw/DBIx::Class/;
use Scalar::Util qw/weaken/;
use Carp::Clan qw/^DBIx::Class/;
__PACKAGE__->mk_group_accessors('simple' => qw/debug debugobj schema/);
package # Hide from PAUSE
    DBIx::Class::Storage::NESTED_ROLLBACK_EXCEPTION;
use overload '"' => sub {
  'DBIx::Class::Storage::NESTED_ROLLBACK_EXCEPTION'
};
sub new {
  my $class = shift;
  my $self = {};
  return bless $self, $class;
}
package DBIx::Class::Storage;
HideShow 19 lines of Pod
=head1 NAME
DBIx::Class::Storage - Generic Storage Handler
=head1 DESCRIPTION
A base implementation of common Storage methods.  For specific
information about L<DBI>-based storage, see L<DBIx::Class::Storage::DBI>.
=head1 METHODS
=head2 new
Arguments: $schema
Instantiates the Storage object.
=cut
sub new {
  my ($self, $schema) = @_;
  $self = ref $self if ref $self;
  my $new = {};
  bless $new, $self;
  $new->set_schema($schema);
  $new->debugobj(new DBIx::Class::Storage::Statistics());
  my $fh;
  my $debug_env = $ENV{DBIX_CLASS_STORAGE_DBI_DEBUG}
                  || $ENV{DBIC_TRACE};
  if (defined($debug_env) && ($debug_env =~ /=(.+)$/)) {
    $fh = IO::File->new($1, 'w')
      or $new->throw_exception("Cannot open trace file $1");
  } else {
    $fh = IO::File->new('>&STDERR');
  }
  $new->debugfh($fh);
  $new->debug(1) if $debug_env;
  $new;
}
HideShow 7 lines of Pod
=head2 set_schema
Used to reset the schema class or object which owns this
storage object, such as during L<DBIx::Class::Schema/clone>.
=cut
sub set_schema {
  my ($self, $schema) = @_;
  $self->schema($schema);
  weaken($self->{schema}) if ref $self->{schema};
}
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=head2 connected
Returns true if we have an open storage connection, false
if it is not (yet) open.
=cut
sub connected { die "Virtual method!" }
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=head2 disconnect
Closes any open storage connection unconditionally.
=cut
sub disconnect { die "Virtual method!" }
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=head2 ensure_connected
Initiate a connection to the storage if one isn't already open.
=cut
sub ensure_connected { die "Virtual method!" }
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=head2 throw_exception
Throws an exception - croaks.
=cut
sub throw_exception {
  my $self = shift;
  $self->schema->throw_exception(@_) if $self->schema;
  croak @_;
}
HideShow 56 lines of Pod
=head2 txn_do
=over 4
=item Arguments: C<$coderef>, @coderef_args?
=item Return Value: The return value of $coderef
=back
Executes C<$coderef> with (optional) arguments C<@coderef_args> atomically,
returning its result (if any). If an exception is caught, a rollback is issued
and the exception is rethrown. If the rollback fails, (i.e. throws an
exception) an exception is thrown that includes a "Rollback failed" message.
For example,
  my $author_rs = $schema->resultset('Author')->find(1);
  my @titles = qw/Night Day It/;
  my $coderef = sub {
    # If any one of these fails, the entire transaction fails
    $author_rs->create_related('books', {
      title => $_
    }) foreach (@titles);
    return $author->books;
  };
  my $rs;
  eval {
    $rs = $schema->txn_do($coderef);
  };
  if ($@) {                                  # Transaction failed
    die "something terrible has happened!"   #
      if ($@ =~ /Rollback failed/);          # Rollback failed
    deal_with_failed_transaction();
  }
In a nested transaction (calling txn_do() from within a txn_do() coderef) only
the outermost transaction will issue a L</txn_commit>, and txn_do() can be
called in void, scalar and list context and it will behave as expected.
Please note that all of the code in your coderef, including non-DBIx::Class
code, is part of a transaction.  This transaction may fail out halfway, or
it may get partially double-executed (in the case that our DB connection
failed halfway through the transaction, in which case we reconnect and
restart the txn).  Therefore it is best that any side-effects in your coderef
are idempotent (that is, can be re-executed multiple times and get the
same result), and that you check up on your side-effects in the case of
transaction failure.
=cut
sub txn_do {
  my ($self, $coderef, @args) = @_;
  ref $coderef eq 'CODE' or $self->throw_exception
    ('$coderef must be a CODE reference');
  my (@return_values, $return_value);
  $self->txn_begin; # If this throws an exception, no rollback is needed
  my $wantarray = wantarray; # Need to save this since the context
                             # inside the eval{} block is independent
                             # of the context that called txn_do()
  eval {
    # Need to differentiate between scalar/list context to allow for
    # returning a list in scalar context to get the size of the list
    if ($wantarray) {
      # list context
      @return_values = $coderef->(@args);
    } elsif (defined $wantarray) {
      # scalar context
      $return_value = $coderef->(@args);
    } else {
      # void context
      $coderef->(@args);
    }
    $self->txn_commit;
  };
  if ($@) {
    my $error = $@;
    eval {
      $self->txn_rollback;
    };
    if ($@) {
      my $rollback_error = $@;
      my $exception_class = "DBIx::Class::Storage::NESTED_ROLLBACK_EXCEPTION";
      $self->throw_exception($error)  # propagate nested rollback
        if $rollback_error =~ /$exception_class/;
      $self->throw_exception(
        "Transaction aborted: $error. Rollback failed: ${rollback_error}"
      );
    } else {
      $self->throw_exception($error); # txn failed but rollback succeeded
    }
  }
  return $wantarray ? @return_values : $return_value;
}
HideShow 9 lines of Pod
=head2 txn_begin
Starts a transaction.
See the preferred L</txn_do> method, which allows for
an entire code block to be executed transactionally.
=cut
sub txn_begin { die "Virtual method!" }
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=head2 txn_commit
Issues a commit of the current transaction.
=cut
sub txn_commit { die "Virtual method!" }
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=head2 txn_rollback
Issues a rollback of the current transaction. A nested rollback will
throw a L<DBIx::Class::Storage::NESTED_ROLLBACK_EXCEPTION> exception,
which allows the rollback to propagate to the outermost transaction.
=cut
sub txn_rollback { die "Virtual method!" }
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=head2 sql_maker
Returns a C<sql_maker> object - normally an object of class
C<DBIC::SQL::Abstract>.
=cut
sub sql_maker { die "Virtual method!" }
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=head2 debug
Causes trace information to be emitted on the C<debugobj> object.
(or C<STDERR> if C<debugobj> has not specifically been set).
This is the equivalent to setting L</DBIC_TRACE> in your
shell environment.
=head2 debugfh
Set or retrieve the filehandle used for trace/debug output.  This should be
an IO::Handle compatible ojbect (only the C<print> method is used.  Initially
set to be STDERR - although see information on the
L<DBIC_TRACE> environment variable.
=cut
sub debugfh {
    my $self = shift;
    if ($self->debugobj->can('debugfh')) {
        return $self->debugobj->debugfh(@_);
    }
}
HideShow 17 lines of Pod
=head2 debugobj
Sets or retrieves the object used for metric collection. Defaults to an instance
of L<DBIx::Class::Storage::Statistics> that is compatible with the original
method of using a coderef as a callback.  See the aforementioned Statistics
class for more information.
=head2 debugcb
Sets a callback to be executed each time a statement is run; takes a sub
reference.  Callback is executed as $sub->($op, $info) where $op is
SELECT/INSERT/UPDATE/DELETE and $info is what would normally be printed.
See L<debugobj> for a better way.
=cut
sub debugcb {
    my $self = shift;
    if ($self->debugobj->can('callback')) {
        return $self->debugobj->callback(@_);
    }
}
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=head2 cursor
The cursor class for this Storage object.
=cut
sub cursor { die "Virtual method!" }
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=head2 deploy
Deploy the tables to storage (CREATE TABLE and friends in a SQL-based
Storage class). This would normally be called through
L<DBIx::Class::Schema/deploy>.
=cut
sub deploy { die "Virtual method!" }
HideShow 11 lines of Pod
=head2 connect_info
The arguments of C<connect_info> are always a single array reference,
and are Storage-handler specific.
This is normally accessed via L<DBIx::Class::Schema/connection>, which
encapsulates its argument list in an arrayref before calling
C<connect_info> here.
=cut
sub connect_info { die "Virtual method!" }
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=head2 select
Handle a select statement.
=cut
sub select { die "Virtual method!" }
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=head2 insert
Handle an insert statement.
=cut
sub insert { die "Virtual method!" }
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=head2 update
Handle an update statement.
=cut
sub update { die "Virtual method!" }
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=head2 delete
Handle a delete statement.
=cut
sub delete { die "Virtual method!" }
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=head2 select_single
Performs a select, fetch and return of data - handles a single row
only.
=cut
sub select_single { die "Virtual method!" }
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=head2 columns_info_for
Returns metadata for the given source's columns.  This
is *deprecated*, and will be removed before 1.0.  You should
be specifying the metadata yourself if you need it.
=cut
sub columns_info_for { die "Virtual method!" }
HideShow 31 lines of Pod
=head1 ENVIRONMENT VARIABLES
=head2 DBIC_TRACE
If C<DBIC_TRACE> is set then trace information
is produced (as when the L<debug> method is set).
If the value is of the form C<1=/path/name> then the trace output is
written to the file C</path/name>.
This environment variable is checked when the storage object is first
created (when you call connect on your schema).  So, run-time changes 
to this environment variable will not take effect unless you also 
re-connect on your schema.
=head2 DBIX_CLASS_STORAGE_DBI_DEBUG
Old name for DBIC_TRACE
=head1 AUTHORS
Matt S. Trout <mst@shadowcatsystems.co.uk>
Andy Grundman <andy@hybridized.org>
=head1 LICENSE
You may distribute this code under the same terms as Perl itself.
=cut
1;