From: Peter Rabbitson <ribasushi@cpan.org>
Date: Sat, 5 Dec 2009 09:29:50 +0000 (+0000)
Subject: Wrap mssql selects in yet another subquery to make limited right-ordered join results... 
X-Git-Tag: v0.08116~103^2~9
X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=commitdiff_plain;h=b8d88d9b31a7bf9b755cc8b396d5c47cb5bcf3fb;p=dbsrgits%2FDBIx-Class.git

Wrap mssql selects in yet another subquery to make limited right-ordered join resultsets possible
---

diff --git a/lib/DBIx/Class/Storage/DBI.pm b/lib/DBIx/Class/Storage/DBI.pm
index 123ecd1..28e3465 100644
--- a/lib/DBIx/Class/Storage/DBI.pm
+++ b/lib/DBIx/Class/Storage/DBI.pm
@@ -1765,12 +1765,52 @@ sub _select_args {
   if (
     ( $attrs->{rows} && keys %{$attrs->{collapse}} )
        ||
-    ( $attrs->{group_by} && @{$attrs->{group_by}} &&
-      $attrs->{_prefetch_select} && @{$attrs->{_prefetch_select}} )
+    ( $attrs->{group_by}
+        &&
+      @{$attrs->{group_by}}
+        &&
+      $attrs->{_prefetch_select}
+        &&
+      @{$attrs->{_prefetch_select}}
+    )
   ) {
+
     ($ident, $select, $where, $attrs)
       = $self->_adjust_select_args_for_complex_prefetch ($ident, $select, $where, $attrs);
   }
+
+  elsif (
+    ($attrs->{rows} || $attrs->{offset})
+      &&
+    ($sql_maker->limit_dialect eq 'RowNumberOver' || $sql_maker->limit_dialect eq 'Top' )
+      &&
+    (ref $ident eq 'ARRAY' && @$ident > 1)  # indicates a join
+      &&
+    scalar $sql_maker->_order_by_chunks ($attrs->{order_by})
+  ) {
+    # the two limit dialects above mangle the SQL such that the join gets lost
+    # wrap a subquery here
+
+    push @limit, delete @{$attrs}{qw/rows offset/};
+
+    my $subq = $self->_select_args_to_query (
+      $ident,
+      $select,
+      $where,
+      $attrs,
+    );
+
+    $ident = {
+      -alias => $attrs->{alias},
+      -source_handle => $ident->[0]{-source_handle},
+      $attrs->{alias} => $subq,
+    };
+
+    # all part of the subquery now
+    delete @{$attrs}{qw/order_by group_by having/};
+    $where = undef;
+  }
+
   elsif (! $attrs->{software_limit} ) {
     push @limit, $attrs->{rows}, $attrs->{offset};
   }
diff --git a/lib/DBIx/Class/Storage/DBI/MSSQL.pm b/lib/DBIx/Class/Storage/DBI/MSSQL.pm
index 28b87f2..cddfc5e 100644
--- a/lib/DBIx/Class/Storage/DBI/MSSQL.pm
+++ b/lib/DBIx/Class/Storage/DBI/MSSQL.pm
@@ -185,27 +185,14 @@ sub last_insert_id { shift->_identity }
 sub _select_args_to_query {
   my $self = shift;
 
-  # _select_args does some shady action at a distance
-  # see DBI.pm for more info
-  my $sql_maker = $self->sql_maker;
-  my ($op, $bind, $ident, $bind_attrs, $select, $cond, $order, $rows, $offset);
-  {
-    local $sql_maker->{_dbic_rs_attrs};
-    ($op, $bind, $ident, $bind_attrs, $select, $cond, $order, $rows, $offset) = $self->_select_args(@_);
-  }
+  my ($sql, $prep_bind, @rest) = $self->next::method (@_);
 
-  if (
-    ($rows || $offset)
-      ||
-    not scalar $sql_maker->_order_by_chunks ($order->{order_by})
-  ) {
-    # either limited RS or no ordering, just short circuit
-    return $self->next::method (@_);
+  # see if this is an ordered subquery
+  my $attrs = $_[3];
+  if ( scalar $self->sql_maker->_order_by_chunks ($attrs->{order_by}) ) {
+    $sql =~ s/^ \s* SELECT \s/SELECT TOP 100 PERCENT /xi;
   }
 
-  my ($sql, $prep_bind, @rest) = $self->next::method (@_);
-  $sql =~ s/^ \s* SELECT \s/SELECT TOP 100 PERCENT /xi;
-
   return wantarray
     ? ($sql, $prep_bind, @rest)
     : \[ "($sql)", @$prep_bind ]
diff --git a/t/746mssql.t b/t/746mssql.t
index e883c22..a261791 100644
--- a/t/746mssql.t
+++ b/t/746mssql.t
@@ -310,8 +310,6 @@ $schema->storage->_sql_maker->{name_sep} = '.';
       prefetch => 'owner',
       rows     => 2,  # 3 results total
       order_by => { -desc => 'owner' },
-      # there is no sane way to order by the right side of a grouped prefetch currently :(
-      #order_by => { -desc => 'owner.name' },
     },
   );
 
@@ -334,6 +332,25 @@ $schema->storage->_sql_maker->{name_sep} = '.';
   is ($books->page(2)->count_rs->next, 1, 'Prefetched grouped search returns correct count_rs');
 }
 
+# make sure right-join-side ordering limit works
+{
+  my $rs = $schema->resultset ('BooksInLibrary')->search (
+    {
+      'owner.name' => [qw/wiggle woggle/],
+    },
+    {
+      join => 'owner',
+      order_by => { -desc => 'owner.name' },
+    }
+  );
+
+  is ($rs->all, 3, 'Correct amount of objects from right-sorted joined resultset');
+  my $limited_rs = $rs->search ({}, {rows => 2, offset => 2});
+  is ($limited_rs->count, 1, 'Correct count of limited right-sorted joined resultset');
+  is ($limited_rs->count_rs->next, 1, 'Correct count_rs of limited right-sorted joined resultset');
+  is ($limited_rs->all, 1, 'Correct amount of objects from limited right-sorted joined resultset');
+}
+
 done_testing;
 
 # clean up our mess