4 files changed, 8 insertions, 8 deletions
diff --git a/activerecord/lib/arel/nodes/bind_param.rb b/activerecord/lib/arel/nodes/bind_param.rb
index 53c5563d93..91e9b2b70f 100644
--- a/activerecord/lib/arel/nodes/bind_param.rb
+++ b/activerecord/lib/arel/nodes/bind_param.rb
@@ -3,7 +3,7 @@
 module Arel # :nodoc: all
   module Nodes
     class BindParam < Node
-      attr_accessor :value
+      attr_reader :value
 
       def initialize(value)
         @value = value
diff --git a/activerecord/lib/arel/select_manager.rb b/activerecord/lib/arel/select_manager.rb
index 22a04b00c6..733176ad9e 100644
--- a/activerecord/lib/arel/select_manager.rb
+++ b/activerecord/lib/arel/select_manager.rb
@@ -252,9 +252,9 @@ module Arel # :nodoc: all
     end
 
     private
-      def collapse(exprs, existing = nil)
-        exprs = exprs.unshift(existing.expr) if existing
-        exprs = exprs.compact.map { |expr|
+      def collapse(exprs)
+        exprs = exprs.compact
+        exprs.map! { |expr|
           if String === expr
             # FIXME: Don't do this automatically
             Arel.sql(expr)
diff --git a/activerecord/lib/arel/visitors/postgresql.rb b/activerecord/lib/arel/visitors/postgresql.rb
index 108ee431ee..c5110fa89c 100644
--- a/activerecord/lib/arel/visitors/postgresql.rb
+++ b/activerecord/lib/arel/visitors/postgresql.rb
@@ -5,7 +5,7 @@ module Arel # :nodoc: all
     class PostgreSQL < Arel::Visitors::ToSql
       CUBE = "CUBE"
       ROLLUP = "ROLLUP"
-      GROUPING_SET = "GROUPING SET"
+      GROUPING_SETS = "GROUPING SETS"
       LATERAL = "LATERAL"
 
       private
@@ -67,7 +67,7 @@ module Arel # :nodoc: all
         end
 
         def visit_Arel_Nodes_GroupingSet(o, collector)
-          collector << GROUPING_SET
+          collector << GROUPING_SETS
           grouping_array_or_grouping_element o, collector
         end
 
diff --git a/activerecord/lib/arel/visitors/to_sql.rb b/activerecord/lib/arel/visitors/to_sql.rb
index 5986fd5576..0682c066fb 100644
--- a/activerecord/lib/arel/visitors/to_sql.rb
+++ b/activerecord/lib/arel/visitors/to_sql.rb
@@ -67,8 +67,8 @@ module Arel # :nodoc: all
         @connection = connection
       end
 
-      def compile(node, &block)
-        accept(node, Arel::Collectors::SQLString.new, &block).value
+      def compile(node, collector = Arel::Collectors::SQLString.new, &block)
+        accept(node, collector, &block).value
       end
 
       private