1 package DBIx::Class::Storage::DBI::MSSQL;
7 DBIx::Class::Storage::DBI::UniqueIdentifier
8 DBIx::Class::Storage::DBI::IdentityInsert
13 use List::Util 'first';
16 __PACKAGE__->mk_group_accessors(simple => qw/
17 _identity _identity_method _no_scope_identity_query
20 __PACKAGE__->sql_maker_class('DBIx::Class::SQLMaker::MSSQL');
22 __PACKAGE__->sql_quote_char([qw/[ ]/]);
24 __PACKAGE__->datetime_parser_type (
25 'DBIx::Class::Storage::DBI::MSSQL::DateTime::Format'
28 __PACKAGE__->new_guid('NEWID()');
30 sub _prep_for_execute {
32 my ($op, $ident, $args) = @_;
34 # cast MONEY values properly
35 if ($op eq 'insert' || $op eq 'update') {
36 my $fields = $args->[0];
38 my $colinfo = $ident->columns_info([keys %$fields]);
40 for my $col (keys %$fields) {
41 # $ident is a result source object with INSERT/UPDATE ops
43 $colinfo->{$col}{data_type}
45 $colinfo->{$col}{data_type} =~ /^money\z/i
47 my $val = $fields->{$col};
48 $fields->{$col} = \['CAST(? AS MONEY)', [ $col => $val ]];
53 my ($sql, $bind) = $self->next::method (@_);
55 # SELECT SCOPE_IDENTITY only works within a statement scope. We
56 # must try to always use this particular idiom first, as it is the
57 # only one that guarantees retrieving the correct id under high
58 # concurrency. When this fails we will fall back to whatever secondary
59 # retrieval method is specified in _identity_method, but at this
60 # point we don't have many guarantees we will get what we expected.
61 # http://msdn.microsoft.com/en-us/library/ms190315.aspx
62 # http://davidhayden.com/blog/dave/archive/2006/01/17/2736.aspx
63 if ($self->_perform_autoinc_retrieval and not $self->_no_scope_identity_query) {
64 $sql .= "\nSELECT SCOPE_IDENTITY()";
73 # always list ctx - we need the $sth
74 my ($rv, $sth, @bind) = $self->next::method(@_);
76 if ($self->_perform_autoinc_retrieval) {
78 # attempt to bring back the result of SELECT SCOPE_IDENTITY() we tacked
79 # on in _prep_for_execute above
82 # we didn't even try on ftds
83 unless ($self->_no_scope_identity_query) {
84 ($identity) = try { $sth->fetchrow_array };
88 # SCOPE_IDENTITY failed, but we can do something else
89 if ( (! $identity) && $self->_identity_method) {
90 ($identity) = $self->_dbh->selectrow_array(
91 'select ' . $self->_identity_method
95 $self->_identity($identity);
98 return wantarray ? ($rv, $sth, @bind) : $rv;
101 sub last_insert_id { shift->_identity }
104 # MSSQL is retarded wrt ordered subselects. One needs to add a TOP
105 # to *all* subqueries, but one also *can't* use TOP 100 PERCENT
106 # http://sqladvice.com/forums/permalink/18496/22931/ShowThread.aspx#22931
108 sub _select_args_to_query {
109 #my ($self, $ident, $select, $cond, $attrs) = @_;
113 my $sql_bind = $self->next::method (@_);
115 # see if this is an ordered subquery
117 $$sql_bind->[0] !~ /^ \s* \( \s* SELECT \s+ TOP \s+ \d+ \s+ /xi
119 scalar $self->_extract_order_criteria ($attrs->{order_by})
121 $self->throw_exception(
122 'An ordered subselect encountered - this is not safe! Please see "Ordered Subselects" in DBIx::Class::Storage::DBI::MSSQL'
123 ) unless $attrs->{unsafe_subselect_ok};
125 $$sql_bind->[0] =~ s/^ \s* \( \s* SELECT (?=\s) / '(SELECT TOP ' . $self->sql_maker->__max_int /exi;
132 # savepoint syntax is the same as in Sybase ASE
134 sub _exec_svp_begin {
135 my ($self, $name) = @_;
137 $self->_dbh->do("SAVE TRANSACTION $name");
140 # A new SAVE TRANSACTION with the same name releases the previous one.
141 sub _exec_svp_release { 1 }
143 sub _exec_svp_rollback {
144 my ($self, $name) = @_;
146 $self->_dbh->do("ROLLBACK TRANSACTION $name");
149 sub sqlt_type { 'SQLServer' }
151 sub sql_limit_dialect {
154 my $supports_rno = 0;
156 if (exists $self->_server_info->{normalized_dbms_version}) {
157 $supports_rno = 1 if $self->_server_info->{normalized_dbms_version} >= 9;
160 # User is connecting via DBD::Sybase and has no permission to run
161 # stored procedures like xp_msver, or version detection failed for some
163 # So, we use a query to check if RNO is implemented.
165 $self->_get_dbh->selectrow_array('SELECT row_number() OVER (ORDER BY rand())');
170 return $supports_rno ? 'RowNumberOver' : 'Top';
176 my $dbh = $self->_dbh or return 0;
178 local $dbh->{RaiseError} = 1;
179 local $dbh->{PrintError} = 0;
182 $dbh->do('select 1');
189 package # hide from PAUSE
190 DBIx::Class::Storage::DBI::MSSQL::DateTime::Format;
192 my $datetime_format = '%Y-%m-%d %H:%M:%S.%3N'; # %F %T
193 my $smalldatetime_format = '%Y-%m-%d %H:%M:%S';
195 my ($datetime_parser, $smalldatetime_parser);
199 require DateTime::Format::Strptime;
200 $datetime_parser ||= DateTime::Format::Strptime->new(
201 pattern => $datetime_format,
204 return $datetime_parser->parse_datetime(shift);
207 sub format_datetime {
209 require DateTime::Format::Strptime;
210 $datetime_parser ||= DateTime::Format::Strptime->new(
211 pattern => $datetime_format,
214 return $datetime_parser->format_datetime(shift);
217 sub parse_smalldatetime {
219 require DateTime::Format::Strptime;
220 $smalldatetime_parser ||= DateTime::Format::Strptime->new(
221 pattern => $smalldatetime_format,
224 return $smalldatetime_parser->parse_datetime(shift);
227 sub format_smalldatetime {
229 require DateTime::Format::Strptime;
230 $smalldatetime_parser ||= DateTime::Format::Strptime->new(
231 pattern => $smalldatetime_format,
234 return $smalldatetime_parser->format_datetime(shift);
241 DBIx::Class::Storage::DBI::MSSQL - Base Class for Microsoft SQL Server support
246 This is the base class for Microsoft SQL Server support, used by
247 L<DBIx::Class::Storage::DBI::ODBC::Microsoft_SQL_Server> and
248 L<DBIx::Class::Storage::DBI::Sybase::Microsoft_SQL_Server>.
250 =head1 IMPLEMENTATION NOTES
252 =head2 IDENTITY information
254 Microsoft SQL Server supports three methods of retrieving the IDENTITY
255 value for inserted row: IDENT_CURRENT, @@IDENTITY, and SCOPE_IDENTITY().
256 SCOPE_IDENTITY is used here because it is the safest. However, it must
257 be called is the same execute statement, not just the same connection.
259 So, this implementation appends a SELECT SCOPE_IDENTITY() statement
260 onto each INSERT to accommodate that requirement.
262 C<SELECT @@IDENTITY> can also be used by issuing:
264 $self->_identity_method('@@identity');
266 it will only be used if SCOPE_IDENTITY() fails.
268 This is more dangerous, as inserting into a table with an on insert trigger that
269 inserts into another table with an identity will give erroneous results on
270 recent versions of SQL Server.
272 =head2 identity insert
274 Be aware that we have tried to make things as simple as possible for our users.
275 For MSSQL that means that when a user tries to create a row, while supplying an
276 explicit value for an autoincrementing column, we will try to issue the
277 appropriate database call to make this possible, namely C<SET IDENTITY_INSERT
278 $table_name ON>. Unfortunately this operation in MSSQL requires the
279 C<db_ddladmin> privilege, which is normally not included in the standard
282 =head2 Ordered Subselects
284 If you attempted the following query (among many others) in Microsoft SQL
288 prefetch => 'relation',
293 You may be surprised to receive an exception. The reason for this is a quirk
294 in the MSSQL engine itself, and sadly doesn't have a sensible workaround due
295 to the way DBIC is built. DBIC can do truly wonderful things with the aid of
296 subselects, and does so automatically when necessary. The list of situations
297 when a subselect is necessary is long and still changes often, so it can not
298 be exhaustively enumerated here. The general rule of thumb is a joined
299 L<has_many|DBIx::Class::Relationship/has_many> relationship with limit/group
300 applied to the left part of the join.
302 In its "pursuit of standards" Microsft SQL Server goes to great lengths to
303 forbid the use of ordered subselects. This breaks a very useful group of
304 searches like "Give me things number 4 to 6 (ordered by name), and prefetch
305 all their relations, no matter how many". While there is a hack which fools
306 the syntax checker, the optimizer may B<still elect to break the subselect>.
307 Testing has determined that while such breakage does occur (the test suite
308 contains an explicit test which demonstrates the problem), it is relative
309 rare. The benefits of ordered subselects are on the other hand too great to be
310 outright disabled for MSSQL.
312 Thus compromise between usability and perfection is the MSSQL-specific
313 L<resultset attribute|DBIx::Class::ResultSet/ATTRIBUTES> C<unsafe_subselect_ok>.
314 It is deliberately not possible to set this on the Storage level, as the user
315 should inspect (and preferably regression-test) the return of every such
316 ResultSet individually. The example above would work if written like:
319 unsafe_subselect_ok => 1,
320 prefetch => 'relation',
325 If it is possible to rewrite the search() in a way that will avoid the need
326 for this flag - you are urged to do so. If DBIC internals insist that an
327 ordered subselect is necessary for an operation, and you believe there is a
328 different/better way to get the same result - please file a bugreport.
332 See L<DBIx::Class/AUTHOR> and L<DBIx::Class/CONTRIBUTORS>.
336 You may distribute this code under the same terms as Perl itself.