KISS - a select(1) makes perfect ordering criteria

[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 1b18b1e..ee2e4cf 100644 (file)
--- a/lib/DBIx/Class/SQLAHacks/MSSQL.pm
+++ b/lib/DBIx/Class/SQLAHacks/MSSQL.pm
@@ -1,33 +1,36 @@
 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/;
 
-#
-# MSSQL is retarded wrt TOP (crappy limit) and ordering.
-# One needs to add a TOP to *all* ordered subqueries, if
-# TOP has been used in the statement at least once.
-# Do it here.
-#
-sub select {
-  my $self = shift;
-
-  my ($sql, @bind) = $self->SUPER::select (@_);
-
-  # ordering was requested and there are at least 2 SELECT/FROM pairs
-  # (thus subquery), and there is no TOP specified
-  if (
-    $sql =~ /\bSELECT\b .+? \bFROM\b .+? \bSELECT\b .+? \bFROM\b/isx
-      &&
-    $sql !~ /^ \s* SELECT \s+ TOP \s+ \d+ /xi
-      &&
-    scalar $self->_order_by_chunks ($_[3]->{order_by})
-  ) {
-    $sql =~ s/^ \s* SELECT \s/SELECT TOP 100 PERCENT /xi;
-  }
-
-  return wantarray ? ($sql, @bind) : $sql;
+# an MSSQL-specific implementation of the Row-Number-Over limiting
+# technique
+
+sub _MSRowNumberOver {
+  my ($self, $sql, $order, $rows, $offset ) = @_;
+
+  # get the order_by only (or make up an order if none exists)
+  my $order_by = $self->_order_by(
+    (delete $order->{order_by}) || \ '(SELECT (1))'
+  );
+
+  # whatever is left
+  my $group_having = $self->_order_by($order);
+
+  $sql = sprintf (<<'EOS', $order_by, $sql, $group_having, $offset + 1, $offset + $rows, );
+
+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
+
+EOS
+
+  $sql =~ s/\s*\n\s*/ /g;   # easier to read in the debugger
+  return $sql;
 }
 
 1;