Unify access to bind values on Relation

The bind values can come from four places. `having`, `where`, `joins`,
and `from` when selecting from a subquery that contains binds. These
need to be kept in a specific order, since the clauses will always
appear in that order. Up until recently, they were not.

Additionally, `joins` actually did keep its bind values in a separate
location (presumably because it's the only case that people noticed was
broken). However, this meant that anything accessing just `bind_values`
was broken (which most places were). This is no longer possible, there
is only a single way to access the bind values, and it includes joins in
the proper location. The setter was removed yesterday, so breaking `+=`
cases is not possible.

I'm still not happy that `joins` is putting it's bind values on the
Arel AST, and I'm planning on refactoring it further, but this removes a
ton of bug cases.

activerecord/lib/active_record/relation.rb

@@ -342,8 +342,7 @@ module ActiveRecord
         stmt.wheres = arel.constraints
       end
 
-      bvs = arel.bind_values + bind_values
-      @klass.connection.update stmt, 'SQL', bvs
+      @klass.connection.update stmt, 'SQL', bind_values
     end
 
     # Updates an object (or multiple objects) and saves it to the database, if validations pass.
@@ -559,11 +558,10 @@ module ActiveRecord
                       find_with_associations { |rel| relation = rel }
                     end
 
-                    arel  = relation.arel
-                    binds = arel.bind_values + relation.bind_values
+                    binds = relation.bind_values
                     binds = connection.prepare_binds_for_database(binds)
                     binds.map! { |_, value| connection.quote(value) }
-                    collect = visitor.accept(arel.ast, Arel::Collectors::Bind.new)
+                    collect = visitor.accept(relation.arel.ast, Arel::Collectors::Bind.new)
                     collect.substitute_binds(binds).join
                   end
     end
@@ -636,7 +634,7 @@ module ActiveRecord
     private
 
     def exec_queries
-      @records = eager_loading? ? find_with_associations : @klass.find_by_sql(arel, arel.bind_values + bind_values)
+      @records = eager_loading? ? find_with_associations : @klass.find_by_sql(arel, bind_values)
 
       preload = preload_values
       preload +=  includes_values unless eager_loading?

activerecord/lib/active_record/relation/calculations.rb

@@ -166,7 +166,7 @@ module ActiveRecord
         relation.select_values = column_names.map { |cn|
           columns_hash.key?(cn) ? arel_table[cn] : cn
         }
-        result = klass.connection.select_all(relation.arel, nil, relation.arel.bind_values + bind_values)
+        result = klass.connection.select_all(relation.arel, nil, bind_values)
         result.cast_values(klass.column_types)
       end
     end
@@ -227,14 +227,11 @@ module ActiveRecord
 
       column_alias = column_name
 
-      bind_values = nil
-
       if operation == "count" && (relation.limit_value || relation.offset_value)
         # Shortcut when limit is zero.
         return 0 if relation.limit_value == 0
 
         query_builder = build_count_subquery(relation, column_name, distinct)
-        bind_values = query_builder.bind_values + relation.bind_values
       else
         column = aggregate_column(column_name)
 
@@ -245,7 +242,6 @@ module ActiveRecord
         relation.select_values = [select_value]
 
         query_builder = relation.arel
-        bind_values = query_builder.bind_values + relation.bind_values
       end
 
       result = @klass.connection.select_all(query_builder, nil, bind_values)
@@ -304,7 +300,7 @@ module ActiveRecord
       relation.group_values  = group
       relation.select_values = select_values
 
-      calculated_data = @klass.connection.select_all(relation, nil, relation.arel.bind_values + bind_values)
+      calculated_data = @klass.connection.select_all(relation, nil, relation.bind_values)
 
       if association
         key_ids     = calculated_data.collect { |row| row[group_aliases.first] }
@@ -378,11 +374,9 @@ module ActiveRecord
 
       aliased_column = aggregate_column(column_name == :all ? 1 : column_name).as(column_alias)
       relation.select_values = [aliased_column]
-      arel = relation.arel
-      subquery = arel.as(subquery_alias)
+      subquery = relation.arel.as(subquery_alias)
 
       sm = Arel::SelectManager.new relation.engine
-      sm.bind_values = arel.bind_values
       select_value = operation_over_aggregate_column(column_alias, 'count', distinct)
       sm.project(select_value).from(subquery)
     end

activerecord/lib/active_record/relation/finder_methods.rb

@@ -311,7 +311,7 @@ module ActiveRecord
         end
       end
 
-      connection.select_value(relation, "#{name} Exists", relation.arel.bind_values + relation.bind_values) ? true : false
+      connection.select_value(relation, "#{name} Exists", relation.bind_values) ? true : false
     end
 
     # This method is called whenever no records are found with either a single
@@ -365,7 +365,7 @@ module ActiveRecord
           []
         else
           arel = relation.arel
-          rows = connection.select_all(arel, 'SQL', arel.bind_values + relation.bind_values)
+          rows = connection.select_all(arel, 'SQL', relation.bind_values)
           join_dependency.instantiate(rows, aliases)
         end
       end
@@ -410,7 +410,7 @@ module ActiveRecord
       relation = relation.except(:select).select(values).distinct!
       arel = relation.arel
 
-      id_rows = @klass.connection.select_all(arel, 'SQL', arel.bind_values + relation.bind_values)
+      id_rows = @klass.connection.select_all(arel, 'SQL', relation.bind_values)
       id_rows.map {|row| row[primary_key]}
     end
 

activerecord/lib/active_record/relation/from_clause.rb

@@ -10,7 +10,7 @@ module ActiveRecord
 
       def binds
         if value.is_a?(Relation)
-          value.arel.bind_values + value.bind_values
+          value.bind_values
         else
           []
         end

activerecord/lib/active_record/relation/predicate_builder.rb

@@ -104,7 +104,7 @@ module ActiveRecord
           result[column_name] = attrs
           binds += bvs
         when Relation
-          binds += value.arel.bind_values + value.bind_values
+          binds += value.bind_values
         else
           if can_be_bound?(column_name, value)
             result[column_name] = Arel::Nodes::BindParam.new

activerecord/lib/active_record/relation/query_methods.rb

@@ -94,7 +94,7 @@ module ActiveRecord
     end
 
     def bind_values
-      from_clause.binds + where_clause.binds + having_clause.binds
+      from_clause.binds + arel.bind_values + where_clause.binds + having_clause.binds
     end
 
     def create_with_value # :nodoc: