Add support for unordered limited resultsets

[dbsrgits/DBIx-Class.git] / lib / DBIx / Class / SQLAHacks / MSSQL.pm

diff --git a/lib/DBIx/Class/SQLAHacks/MSSQL.pm b/lib/DBIx/Class/SQLAHacks/MSSQL.pm
index 70cc8c3..20105a8 100644 (file)
--- a/lib/DBIx/Class/SQLAHacks/MSSQL.pm
+++ b/lib/DBIx/Class/SQLAHacks/MSSQL.pm
@@ -1,27 +1,45 @@
 package # Hide from PAUSE
   DBIx::Class::SQLAHacks::MSSQL;
 
+use warnings;
+use strict;
+
 use base qw( DBIx::Class::SQLAHacks );
 use Carp::Clan qw/^DBIx::Class|^SQL::Abstract/;
 
-sub _RowNumberOver {
+# an MSSQL-specific implementation of the Row-Number-Over limiting
+# technique
+
+sub _MSRowNumberOver {
   my ($self, $sql, $order, $rows, $offset ) = @_;
 
-  $offset += 1;
-  my $last = $rows + $offset - 1;
-  my ( $order_by ) = $self->_order_by( $order );
+  # get the order_by only
+  my $order_by = $self->_order_by(
+    (delete $order->{order_by}) || do {
+
+      # no order was supplied - make something up:
+      my $rsrc = $self->{_dbic_rs_attrs}{_source_handle}->resolve;
+      if (my @pk = $rsrc->primary_columns) {
+        \@pk;
+      }
+      else {
+        [($rsrc->columns)[0]];
+      }
+    }
+  );
+
+  # whatever is left
+  my $group_having = $self->_order_by($order);
+
+  $sql = sprintf (<<'EOS', $order_by, $sql, $group_having, $offset + 1, $offset + $rows, );
 
-  $sql = <<"SQL";
-SELECT * FROM
-(
-   SELECT Q1.*, ROW_NUMBER() OVER( $order_by ) AS ROW_NUM FROM (
-      $sql
-   ) Q1
-) Q2
-WHERE ROW_NUM BETWEEN $offset AND $last
+SELECT * FROM (
+  SELECT orig_query.*, ROW_NUMBER() OVER(%s ) AS rno__row__index FROM (%s%s) orig_query
+) rno_subq WHERE rno__row__index BETWEEN %d AND %d
 
-SQL
+EOS
 
+  $sql =~ s/\s*\n\s*/ /g;   # easier to read in the debugger
   return $sql;
 }