X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=lib%2FDBIx%2FClass%2FStorage%2FDBI%2FMSSQL.pm;h=fedec7fa423533f1b36c0e65a3d61ee765b92f96;hb=0777ad33930b2c09258f9752e4e76c27ca75f347;hp=874255910411789e749b591c37d15cd0ce46f741;hpb=be294d66f165fa65c7663dc5015503516e74e419;p=dbsrgits%2FDBIx-Class.git

diff --git a/lib/DBIx/Class/Storage/DBI/MSSQL.pm b/lib/DBIx/Class/Storage/DBI/MSSQL.pm
index 8742559..fedec7f 100644
--- a/lib/DBIx/Class/Storage/DBI/MSSQL.pm
+++ b/lib/DBIx/Class/Storage/DBI/MSSQL.pm
@@ -3,7 +3,7 @@ package DBIx::Class::Storage::DBI::MSSQL;
 use strict;
 use warnings;
 
-use base qw/DBIx::Class::Storage::DBI::AmbiguousGlob DBIx::Class::Storage::DBI/;
+use base qw/DBIx::Class::Storage::DBI/;
 use mro 'c3';
 
 use List::Util();
@@ -14,30 +14,55 @@ __PACKAGE__->mk_group_accessors(simple => qw/
 
 __PACKAGE__->sql_maker_class('DBIx::Class::SQLAHacks::MSSQL');
 
+sub _set_identity_insert {
+  my ($self, $table) = @_;
+
+  my $sql = sprintf (
+    'SET IDENTITY_INSERT %s ON',
+    $self->sql_maker->_quote ($table),
+  );
+
+  my $dbh = $self->_get_dbh;
+  eval { $dbh->do ($sql) };
+  if ($@) {
+    $self->throw_exception (sprintf "Error executing '%s': %s",
+      $sql,
+      $dbh->errstr,
+    );
+  }
+}
+
+sub _unset_identity_insert {
+  my ($self, $table) = @_;
+
+  my $sql = sprintf (
+    'SET IDENTITY_INSERT %s OFF',
+    $self->sql_maker->_quote ($table),
+  );
+
+  my $dbh = $self->_get_dbh;
+  $dbh->do ($sql);
+}
+
 sub insert_bulk {
   my $self = shift;
   my ($source, $cols, $data) = @_;
 
-  my $identity_insert = 0;
+  my $is_identity_insert = (List::Util::first
+      { $source->column_info ($_)->{is_auto_increment} }
+      (@{$cols})
+  )
+     ? 1
+     : 0;
 
-  COLUMNS:
-  foreach my $col (@{$cols}) {
-    if ($source->column_info($col)->{is_auto_increment}) {
-      $identity_insert = 1;
-      last COLUMNS;
-    }
-  }
-
-  if ($identity_insert) {
-    my $table = $source->from;
-    $self->_get_dbh->do("SET IDENTITY_INSERT $table ON");
+  if ($is_identity_insert) {
+     $self->_set_identity_insert ($source->name);
   }
 
   $self->next::method(@_);
 
-  if ($identity_insert) {
-    my $table = $source->from;
-    $self->_get_dbh->do("SET IDENTITY_INSERT $table OFF");
+  if ($is_identity_insert) {
+     $self->_unset_identity_insert ($source->name);
   }
 }
 
@@ -47,7 +72,7 @@ sub insert {
   my $self = shift;
   my ($source, $to_insert) = @_;
 
-  my $updated_cols = {};
+  my $supplied_col_info = $self->_resolve_column_info($source, [keys %$to_insert] );
 
   my %guid_cols;
   my @pk_cols = $source->primary_columns;
@@ -71,13 +96,28 @@ sub insert {
   my @get_guids_for =
     grep { not exists $to_insert->{$_} } (@pk_guids, @auto_guids);
 
+  my $updated_cols = {};
+
   for my $guid_col (@get_guids_for) {
     my ($new_guid) = $self->_get_dbh->selectrow_array('SELECT NEWID()');
     $updated_cols->{$guid_col} = $to_insert->{$guid_col} = $new_guid;
   }
 
+  my $is_identity_insert = (List::Util::first { $_->{is_auto_increment} } (values %$supplied_col_info) )
+     ? 1
+     : 0;
+
+  if ($is_identity_insert) {
+     $self->_set_identity_insert ($source->name);
+  }
+
   $updated_cols = { %$updated_cols, %{ $self->next::method(@_) } };
 
+  if ($is_identity_insert) {
+     $self->_unset_identity_insert ($source->name);
+  }
+
+
   return $updated_cols;
 }
 
@@ -105,14 +145,6 @@ sub _prep_for_execute {
   if ($op eq 'insert') {
     $sql .= ';SELECT SCOPE_IDENTITY()';
 
-    my $col_info = $self->_resolve_column_info($ident, [map $_->[0], @{$bind}]);
-    if (List::Util::first { $_->{is_auto_increment} } (values %$col_info) ) {
-
-      my $table = $ident->from;
-      my $identity_insert_on = "SET IDENTITY_INSERT $table ON";
-      my $identity_insert_off = "SET IDENTITY_INSERT $table OFF";
-      $sql = "$identity_insert_on; $sql; $identity_insert_off";
-    }
   }
 
   return ($sql, $bind);
@@ -128,7 +160,7 @@ sub _execute {
 
     # this should bring back the result of SELECT SCOPE_IDENTITY() we tacked
     # on in _prep_for_execute above
-    my ($identity) = $sth->fetchrow_array;
+    my ($identity) = eval { $sth->fetchrow_array };
 
     # SCOPE_IDENTITY failed, but we can do something else
     if ( (! $identity) && $self->_identity_method) {
@@ -146,6 +178,33 @@ sub _execute {
 
 sub last_insert_id { shift->_identity }
 
+#
+# MSSQL is retarded wrt ordered subselects. One needs to add a TOP
+# to *all* subqueries, but one also can't use TOP 100 PERCENT
+# http://sqladvice.com/forums/permalink/18496/22931/ShowThread.aspx#22931
+#
+sub _select_args_to_query {
+  my $self = shift;
+
+  my ($sql, $prep_bind, @rest) = $self->next::method (@_);
+
+  # see if this is an ordered subquery
+  my $attrs = $_[3];
+  if ( scalar $self->_parse_order_by ($attrs->{order_by}) ) {
+    $self->throw_exception(
+      'An ordered subselect encountered - this is not safe! Please see "Ordered Subselects" in DBIx::Class::Storage::DBI::MSSQL
+    ') unless $attrs->{unsafe_subselect_ok};
+    my $max = 2 ** 32;
+    $sql =~ s/^ \s* SELECT \s/SELECT TOP $max /xi;
+  }
+
+  return wantarray
+    ? ($sql, $prep_bind, @rest)
+    : \[ "($sql)", @$prep_bind ]
+  ;
+}
+
+
 # savepoint syntax is the same as in Sybase ASE
 
 sub _svp_begin {
@@ -173,14 +232,35 @@ sub build_datetime_parser {
 
 sub sqlt_type { 'SQLServer' }
 
-sub _sql_maker_opts {
-  my ( $self, $opts ) = @_;
+sub _get_mssql_version {
+  my $self = shift;
+
+  my $data = $self->_get_dbh->selectrow_hashref('xp_msver ProductVersion');
 
-  if ( $opts ) {
-    $self->{_sql_maker_opts} = { %$opts };
+  if ($data->{Character_Value} =~ /^(\d+)\./) {
+    return $1;
+  } else {
+    $self->throw_exception(q{Your ProductVersion's Character_Value is missing or malformed!});
+  }
+}
+
+sub sql_maker {
+  my $self = shift;
+
+  unless ($self->_sql_maker) {
+    unless ($self->{_sql_maker_opts}{limit_dialect}) {
+      my $version = eval { $self->_get_mssql_version; } || 0;
+
+      $self->{_sql_maker_opts} = {
+        limit_dialect => ($version >= 9 ? 'RowNumberOver' : 'Top'),
+        %{$self->{_sql_maker_opts}||{}}
+      };
+    }
+
+    my $maker = $self->next::method (@_);
   }
 
-  return { limit_dialect => 'Top', %{$self->{_sql_maker_opts}||{}} };
+  return $self->_sql_maker;
 }
 
 1;
@@ -198,6 +278,8 @@ L<DBIx::Class::Storage::DBI::Sybase::Microsoft_SQL_Server>.
 
 =head1 IMPLEMENTATION NOTES
 
+=head2 IDENTITY information
+
 Microsoft SQL Server supports three methods of retrieving the IDENTITY
 value for inserted row: IDENT_CURRENT, @@IDENTITY, and SCOPE_IDENTITY().
 SCOPE_IDENTITY is used here because it is the safest.  However, it must
@@ -216,6 +298,64 @@ This is more dangerous, as inserting into a table with an on insert trigger that
 inserts into another table with an identity will give erroneous results on
 recent versions of SQL Server.
 
+=head2 identity insert
+
+Be aware that we have tried to make things as simple as possible for our users.
+For MSSQL that means that when a user tries to create a row, while supplying an
+explicit value for an autoincrementing column, we will try to issue the
+appropriate database call to make this possible, namely C<SET IDENTITY_INSERT
+$table_name ON>. Unfortunately this operation in MSSQL requires the
+C<db_ddladmin> privilege, which is normally not included in the standard
+write-permissions.
+
+=head2 Ordered Subselects
+
+If you attempted the following query (among many others) in Microsoft SQL
+Server
+
+ $rs->search ({}, {
+  prefetch => 'relation',
+  rows => 2,
+  offset => 3,
+ });
+
+You may be surprised to receive an exception. The reason for this is a quirk
+in the MSSQL engine itself, and sadly doesn't have a sensible workaround due
+to the way DBIC is built. DBIC can do truly wonderful things with the aid of
+subselects, and does so automatically when necessary. The list of situations
+when a subselect is necessary is long and still changes often, so it can not
+be exhaustively enumerated here. The general rule of thumb is a joined
+L<has_many|DBIx::Class::Relationship/has_many> relationship with limit/group
+applied to the left part of the join.
+
+In its "pursuit of standards" Microsft SQL Server goes to great lengths to
+forbid the use of ordered subselects. This breaks a very useful group of
+searches like "Give me things number 4 to 6 (ordered by name), and prefetch
+all their relations, no matter how many". While there is a hack which fools
+the syntax checker, the optimizer may B<still elect to break the subselect>.
+Testing has determined that while such breakage does occur (the test suite
+contains an explicit test which demonstrates the problem), it is relative
+rare. The benefits of ordered subselects are on the other hand too great to be
+outright disabled for MSSQL.
+
+Thus compromise between usability and perfection is the MSSQL-specific
+L<resultset attribute|DBIx::Class::ResultSet/ATTRIBUTES> C<unsafe_subselect_ok>.
+It is deliberately not possible to set this on the Storage level, as the user
+should inspect (and preferrably regression-test) the return of every such
+ResultSet individually. The example above would work if written like:
+
+ $rs->search ({}, {
+  unsafe_subselect_ok => 1,
+  prefetch => 'relation',
+  rows => 2,
+  offset => 3,
+ });
+
+If it is possible to rewrite the search() in a way that will avoid the need
+for this flag - you are urged to do so. If DBIC internals insist that an
+ordered subselect is necessary for an operation, and you believe there is a
+differnt/better way to get the same result - please file a bugreport.
+
 =head1 AUTHOR
 
 See L<DBIx::Class/CONTRIBUTORS>.