1 package DBIx::Class::Storage::DBI::MSSQL;
7 DBIx::Class::Storage::DBI::UniqueIdentifier
8 DBIx::Class::Storage::DBI::IdentityInsert
12 use DBIx::Class::_Util 'dbic_internal_try';
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) = dbic_internal_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');
190 package # hide from PAUSE
191 DBIx::Class::Storage::DBI::MSSQL::DateTime::Format;
193 my $datetime_format = '%Y-%m-%d %H:%M:%S.%3N'; # %F %T
194 my $smalldatetime_format = '%Y-%m-%d %H:%M:%S';
196 my ($datetime_parser, $smalldatetime_parser);
200 require DateTime::Format::Strptime;
201 $datetime_parser ||= DateTime::Format::Strptime->new(
202 pattern => $datetime_format,
205 return $datetime_parser->parse_datetime(shift);
208 sub format_datetime {
210 require DateTime::Format::Strptime;
211 $datetime_parser ||= DateTime::Format::Strptime->new(
212 pattern => $datetime_format,
215 return $datetime_parser->format_datetime(shift);
218 sub parse_smalldatetime {
220 require DateTime::Format::Strptime;
221 $smalldatetime_parser ||= DateTime::Format::Strptime->new(
222 pattern => $smalldatetime_format,
225 return $smalldatetime_parser->parse_datetime(shift);
228 sub format_smalldatetime {
230 require DateTime::Format::Strptime;
231 $smalldatetime_parser ||= DateTime::Format::Strptime->new(
232 pattern => $smalldatetime_format,
235 return $smalldatetime_parser->format_datetime(shift);
242 DBIx::Class::Storage::DBI::MSSQL - Base Class for Microsoft SQL Server support
247 This is the base class for Microsoft SQL Server support, used by
248 L<DBIx::Class::Storage::DBI::ODBC::Microsoft_SQL_Server> and
249 L<DBIx::Class::Storage::DBI::Sybase::Microsoft_SQL_Server>.
251 =head1 IMPLEMENTATION NOTES
253 =head2 IDENTITY information
255 Microsoft SQL Server supports three methods of retrieving the IDENTITY
256 value for inserted row: IDENT_CURRENT, @@IDENTITY, and SCOPE_IDENTITY().
257 SCOPE_IDENTITY is used here because it is the safest. However, it must
258 be called is the same execute statement, not just the same connection.
260 So, this implementation appends a SELECT SCOPE_IDENTITY() statement
261 onto each INSERT to accommodate that requirement.
263 C<SELECT @@IDENTITY> can also be used by issuing:
265 $self->_identity_method('@@identity');
267 it will only be used if SCOPE_IDENTITY() fails.
269 This is more dangerous, as inserting into a table with an on insert trigger that
270 inserts into another table with an identity will give erroneous results on
271 recent versions of SQL Server.
273 =head2 identity insert
275 Be aware that we have tried to make things as simple as possible for our users.
276 For MSSQL that means that when a user tries to create a row, while supplying an
277 explicit value for an autoincrementing column, we will try to issue the
278 appropriate database call to make this possible, namely C<SET IDENTITY_INSERT
279 $table_name ON>. Unfortunately this operation in MSSQL requires the
280 C<db_ddladmin> privilege, which is normally not included in the standard
283 =head2 Ordered Subselects
285 If you attempted the following query (among many others) in Microsoft SQL
289 prefetch => 'relation',
294 You may be surprised to receive an exception. The reason for this is a quirk
295 in the MSSQL engine itself, and sadly doesn't have a sensible workaround due
296 to the way DBIC is built. DBIC can do truly wonderful things with the aid of
297 subselects, and does so automatically when necessary. The list of situations
298 when a subselect is necessary is long and still changes often, so it can not
299 be exhaustively enumerated here. The general rule of thumb is a joined
300 L<has_many|DBIx::Class::Relationship/has_many> relationship with limit/group
301 applied to the left part of the join.
303 In its "pursuit of standards" Microsft SQL Server goes to great lengths to
304 forbid the use of ordered subselects. This breaks a very useful group of
305 searches like "Give me things number 4 to 6 (ordered by name), and prefetch
306 all their relations, no matter how many". While there is a hack which fools
307 the syntax checker, the optimizer may B<still elect to break the subselect>.
308 Testing has determined that while such breakage does occur (the test suite
309 contains an explicit test which demonstrates the problem), it is relative
310 rare. The benefits of ordered subselects are on the other hand too great to be
311 outright disabled for MSSQL.
313 Thus compromise between usability and perfection is the MSSQL-specific
314 L<resultset attribute|DBIx::Class::ResultSet/ATTRIBUTES> C<unsafe_subselect_ok>.
315 It is deliberately not possible to set this on the Storage level, as the user
316 should inspect (and preferably regression-test) the return of every such
317 ResultSet individually. The example above would work if written like:
320 unsafe_subselect_ok => 1,
321 prefetch => 'relation',
326 If it is possible to rewrite the search() in a way that will avoid the need
327 for this flag - you are urged to do so. If DBIC internals insist that an
328 ordered subselect is necessary for an operation, and you believe there is a
329 different/better way to get the same result - please file a bugreport.
331 =head1 FURTHER QUESTIONS?
333 Check the list of L<additional DBIC resources|DBIx::Class/GETTING HELP/SUPPORT>.
335 =head1 COPYRIGHT AND LICENSE
337 This module is free software L<copyright|DBIx::Class/COPYRIGHT AND LICENSE>
338 by the L<DBIx::Class (DBIC) authors|DBIx::Class/AUTHORS>. You can
339 redistribute it and/or modify it under the same terms as the
340 L<DBIx::Class library|DBIx::Class/COPYRIGHT AND LICENSE>.