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=head1 NAME

DBIx::Class::Storage::DBI::ADO::Microsoft_SQL_Server - Support for Microsoft
SQL Server via DBD::ADO

=head1 SYNOPSIS

This subclass supports MSSQL server connections via L<DBD::ADO>.

=head1 DESCRIPTION

The MSSQL specific functionality is provided by
L<DBIx::Class::Storage::DBI::MSSQL>.

=head1 EXAMPLE DSN

  dbi:ADO:provider=sqlncli10;server=EEEBOX\SQLEXPRESS

=head1 CAVEATS

=head2 identities

C<_identity_method> is set to C<@@identity>, as C<SCOPE_IDENTITY()> doesn't work
with L<DBD::ADO>. See L<DBIx::Class::Storage::DBI::MSSQL/IMPLEMENTATION NOTES>
for caveats regarding this.

=head2 truncation bug

There is a bug with MSSQL ADO providers where data gets truncated based on the
size of the bind sizes in the first prepare call:

L<https://rt.cpan.org/Ticket/Display.html?id=52048>

The C<ado_size> workaround is used (see L<DBD::ADO/ADO providers>) with the
approximate maximum size of the data_type of the bound column, or 8000 (maximum
VARCHAR size) if the data_type is not available.

Please report problems with this driver and send patches.

=head2 LongReadLen

C<LongReadLen> is set to C<LongReadLen * 2 + 1> on connection as it is necessary
for some LOB types. Be aware of this if you localize this value on the C<$dbh>
directly.

=head2 binary data

Due perhaps to the ado_size workaround we use, and/or other reasons, binary data
such as C<varbinary> column data comes back padded with trailing C<NULL> chars.
The Cursor class for this driver
(L<DBIx::Class::Storage::DBI::ADO::Microsoft_SQL_Server::Cursor>) removes them,
of course if your binary data is actually C<NULL> padded that may be an issue to
keep in mind when using this driver.

=head2 uniqueidentifier columns

uniqueidentifier columns come back from ADO wrapped in braces and must be
submitted to the MSSQL ADO driver wrapped in braces. We take care of this
transparently in this driver and the associated Cursor class
(L<DBIx::Class::Storage::DBI::ADO::Microsoft_SQL_Server::Cursor>) so that you
don't have to use braces in most cases (except in literal SQL, in those cases
you will have to add the braces yourself.)

=head2 fractional seconds

Fractional seconds with L<DBIx::Class::InflateColumn::DateTime> are not
currently supported, datetimes are truncated at the second.

=cut

sub _init {
  my $self = shift;

# SCOPE_IDENTITY() doesn't work
  $self->_identity_method('@@identity');
  $self->_no_scope_identity_query(1);

  return $self->next::method(@_);
}

sub _run_connection_actions {
  my $self = shift;

# make transactions work
  require DBD::ADO::Const;
  $self->_dbh->{ado_conn}{CursorLocation} =
    DBD::ADO::Const->Enums->{CursorLocationEnum}{adUseClient};

# set LongReadLen = LongReadLen * 2 + 1
# this may need to be in ADO.pm, being conservative for now...
  my $long_read_len = $self->_dbh->{LongReadLen};

# This is the DBD::ADO default.
  if ($long_read_len != 2147483647) {
    $self->_dbh->{LongReadLen} = $long_read_len * 2 + 1;
  }

  return $self->next::method(@_);
}


# Fix up binary data and GUIDs for ->find, for cursors see the cursor_class
# above.
sub select_single {
  my $self = shift;
  my ($ident, $select) = @_;

  my @row = $self->next::method(@_);

  return @row unless $self->cursor_class->isa(
    'DBIx::Class::Storage::DBI::ADO::Microsoft_SQL_Server::Cursor'
  );

  my $col_infos = $self->_resolve_column_info($ident);

  _normalize_guids($select, $col_infos, \@row, $self);

  _strip_trailing_binary_nulls($select, $col_infos, \@row, $self);