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) = $self->next::method (@_);
55 # SELECT SCOPE_IDENTITY only works within a statement scope. We
56 # must try to always use this particular idiom frist, as it is the
57 # only one that guarantees retrieving the correct id under high
58 # concurrency. When this fails we will fall back to whatever secondary
59 # retrieval method is specified in _identity_method, but at this
60 # point we don't have many guarantees we will get what we expected.
61 # http://msdn.microsoft.com/en-us/library/ms190315.aspx
62 # http://davidhayden.com/blog/dave/archive/2006/01/17/2736.aspx
63 if ($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) : $rv;
101 sub last_insert_id { shift->_identity }
104 # MSSQL is retarded wrt ordered subselects. One needs to add a TOP
105 # to *all* subqueries, but one also *can't* use TOP 100 PERCENT
106 # http://sqladvice.com/forums/permalink/18496/22931/ShowThread.aspx#22931
108 sub _select_args_to_query {
111 my ($sql, $prep_bind, @rest) = $self->next::method (@_);
113 # see if this is an ordered subquery
116 $sql !~ /^ \s* SELECT \s+ TOP \s+ \d+ \s+ /xi
118 scalar $self->_extract_order_criteria ($attrs->{order_by})
120 $self->throw_exception(
121 'An ordered subselect encountered - this is not safe! Please see "Ordered Subselects" in DBIx::Class::Storage::DBI::MSSQL
122 ') unless $attrs->{unsafe_subselect_ok};
123 my $max = $self->sql_maker->__max_int;
124 $sql =~ s/^ \s* SELECT \s/SELECT TOP $max /xi;
128 ? ($sql, $prep_bind, @rest)
129 : \[ "($sql)", @$prep_bind ]
134 # savepoint syntax is the same as in Sybase ASE
136 sub _exec_svp_begin {
137 my ($self, $name) = @_;
139 $self->_dbh->do("SAVE TRANSACTION $name");
142 # A new SAVE TRANSACTION with the same name releases the previous one.
143 sub _exec_svp_release { 1 }
145 sub _exec_svp_rollback {
146 my ($self, $name) = @_;
148 $self->_dbh->do("ROLLBACK TRANSACTION $name");
151 sub sqlt_type { 'SQLServer' }
153 sub sql_limit_dialect {
156 my $supports_rno = 0;
158 if (exists $self->_server_info->{normalized_dbms_version}) {
159 $supports_rno = 1 if $self->_server_info->{normalized_dbms_version} >= 9;
162 # User is connecting via DBD::Sybase and has no permission to run
163 # stored procedures like xp_msver, or version detection failed for some
165 # So, we use a query to check if RNO is implemented.
167 $self->_get_dbh->selectrow_array('SELECT row_number() OVER (ORDER BY rand())');
172 return $supports_rno ? 'RowNumberOver' : 'Top';
178 my $dbh = $self->_dbh or return 0;
180 local $dbh->{RaiseError} = 1;
181 local $dbh->{PrintError} = 0;
184 $dbh->do('select 1');
191 package # hide from PAUSE
192 DBIx::Class::Storage::DBI::MSSQL::DateTime::Format;
194 my $datetime_format = '%Y-%m-%d %H:%M:%S.%3N'; # %F %T
195 my $smalldatetime_format = '%Y-%m-%d %H:%M:%S';
197 my ($datetime_parser, $smalldatetime_parser);
201 require DateTime::Format::Strptime;
202 $datetime_parser ||= DateTime::Format::Strptime->new(
203 pattern => $datetime_format,
206 return $datetime_parser->parse_datetime(shift);
209 sub format_datetime {
211 require DateTime::Format::Strptime;
212 $datetime_parser ||= DateTime::Format::Strptime->new(
213 pattern => $datetime_format,
216 return $datetime_parser->format_datetime(shift);
219 sub parse_smalldatetime {
221 require DateTime::Format::Strptime;
222 $smalldatetime_parser ||= DateTime::Format::Strptime->new(
223 pattern => $smalldatetime_format,
226 return $smalldatetime_parser->parse_datetime(shift);
229 sub format_smalldatetime {
231 require DateTime::Format::Strptime;
232 $smalldatetime_parser ||= DateTime::Format::Strptime->new(
233 pattern => $smalldatetime_format,
236 return $smalldatetime_parser->format_datetime(shift);
243 DBIx::Class::Storage::DBI::MSSQL - Base Class for Microsoft SQL Server support
248 This is the base class for Microsoft SQL Server support, used by
249 L<DBIx::Class::Storage::DBI::ODBC::Microsoft_SQL_Server> and
250 L<DBIx::Class::Storage::DBI::Sybase::Microsoft_SQL_Server>.
252 =head1 IMPLEMENTATION NOTES
254 =head2 IDENTITY information
256 Microsoft SQL Server supports three methods of retrieving the IDENTITY
257 value for inserted row: IDENT_CURRENT, @@IDENTITY, and SCOPE_IDENTITY().
258 SCOPE_IDENTITY is used here because it is the safest. However, it must
259 be called is the same execute statement, not just the same connection.
261 So, this implementation appends a SELECT SCOPE_IDENTITY() statement
262 onto each INSERT to accommodate that requirement.
264 C<SELECT @@IDENTITY> can also be used by issuing:
266 $self->_identity_method('@@identity');
268 it will only be used if SCOPE_IDENTITY() fails.
270 This is more dangerous, as inserting into a table with an on insert trigger that
271 inserts into another table with an identity will give erroneous results on
272 recent versions of SQL Server.
274 =head2 identity insert
276 Be aware that we have tried to make things as simple as possible for our users.
277 For MSSQL that means that when a user tries to create a row, while supplying an
278 explicit value for an autoincrementing column, we will try to issue the
279 appropriate database call to make this possible, namely C<SET IDENTITY_INSERT
280 $table_name ON>. Unfortunately this operation in MSSQL requires the
281 C<db_ddladmin> privilege, which is normally not included in the standard
284 =head2 Ordered Subselects
286 If you attempted the following query (among many others) in Microsoft SQL
290 prefetch => 'relation',
295 You may be surprised to receive an exception. The reason for this is a quirk
296 in the MSSQL engine itself, and sadly doesn't have a sensible workaround due
297 to the way DBIC is built. DBIC can do truly wonderful things with the aid of
298 subselects, and does so automatically when necessary. The list of situations
299 when a subselect is necessary is long and still changes often, so it can not
300 be exhaustively enumerated here. The general rule of thumb is a joined
301 L<has_many|DBIx::Class::Relationship/has_many> relationship with limit/group
302 applied to the left part of the join.
304 In its "pursuit of standards" Microsft SQL Server goes to great lengths to
305 forbid the use of ordered subselects. This breaks a very useful group of
306 searches like "Give me things number 4 to 6 (ordered by name), and prefetch
307 all their relations, no matter how many". While there is a hack which fools
308 the syntax checker, the optimizer may B<still elect to break the subselect>.
309 Testing has determined that while such breakage does occur (the test suite
310 contains an explicit test which demonstrates the problem), it is relative
311 rare. The benefits of ordered subselects are on the other hand too great to be
312 outright disabled for MSSQL.
314 Thus compromise between usability and perfection is the MSSQL-specific
315 L<resultset attribute|DBIx::Class::ResultSet/ATTRIBUTES> C<unsafe_subselect_ok>.
316 It is deliberately not possible to set this on the Storage level, as the user
317 should inspect (and preferably regression-test) the return of every such
318 ResultSet individually. The example above would work if written like:
321 unsafe_subselect_ok => 1,
322 prefetch => 'relation',
327 If it is possible to rewrite the search() in a way that will avoid the need
328 for this flag - you are urged to do so. If DBIC internals insist that an
329 ordered subselect is necessary for an operation, and you believe there is a
330 different/better way to get the same result - please file a bugreport.
334 See L<DBIx::Class/AUTHOR> and L<DBIx::Class/CONTRIBUTORS>.
338 You may distribute this code under the same terms as Perl itself.