Improve compile_update and compile_delete

To be used from `update_all` and `delete_all`.

activerecord/lib/active_record/relation.rb

@@ -469,14 +469,6 @@ module ActiveRecord
         return relation.update_all(updates)
       end
 
-      stmt = Arel::UpdateManager.new
-      stmt.table(arel.join_sources.empty? ? table : arel.source)
-      stmt.key = table[primary_key]
-      stmt.take(arel.limit)
-      stmt.offset(arel.offset)
-      stmt.order(*arel.orders)
-      stmt.wheres = arel.constraints
-
       if updates.is_a?(Hash)
         if klass.locking_enabled? &&
             !updates.key?(klass.locking_column) &&
@@ -484,12 +476,14 @@ module ActiveRecord
           attr = table[klass.locking_column]
           updates[attr.name] = _increment_attribute(attr)
         end
-        stmt.set _substitute_values(updates)
+        values = _substitute_values(updates)
       else
-        stmt.set Arel.sql(klass.sanitize_sql_for_assignment(updates, table.name))
+        values = Arel.sql(klass.sanitize_sql_for_assignment(updates, table.name))
       end
 
-      @klass.connection.update stmt, "#{@klass} Update All"
+      stmt = arel.compile_update(values, table[primary_key])
+
+      klass.connection.update(stmt, "#{klass} Update All")
     end
 
     def update(id = :all, attributes) # :nodoc:
@@ -611,15 +605,9 @@ module ActiveRecord
         return relation.delete_all
       end
 
-      stmt = Arel::DeleteManager.new
-      stmt.from(arel.join_sources.empty? ? table : arel.source)
-      stmt.key = table[primary_key]
-      stmt.take(arel.limit)
-      stmt.offset(arel.offset)
-      stmt.order(*arel.orders)
-      stmt.wheres = arel.constraints
+      stmt = arel.compile_delete(table[primary_key])
 
-      affected = @klass.connection.delete(stmt, "#{@klass} Destroy")
+      affected = klass.connection.delete(stmt, "#{klass} Destroy")
 
       reset
       affected

activerecord/lib/arel/crud.rb

@@ -4,23 +4,6 @@ module Arel # :nodoc: all
   ###
   # FIXME hopefully we can remove this
   module Crud
-    def compile_update(values, pk)
-      um = UpdateManager.new
-
-      if Nodes::SqlLiteral === values
-        relation = @ctx.from
-      else
-        relation = values.first.first.relation
-      end
-      um.key = pk
-      um.table relation
-      um.set values
-      um.take @ast.limit.expr if @ast.limit
-      um.order(*@ast.orders)
-      um.wheres = @ctx.wheres
-      um
-    end
-
     def compile_insert(values)
       im = create_insert
       im.insert values
@@ -31,11 +14,24 @@ module Arel # :nodoc: all
       InsertManager.new
     end
 
-    def compile_delete
-      dm = DeleteManager.new
-      dm.take @ast.limit.expr if @ast.limit
-      dm.wheres = @ctx.wheres
-      dm.from @ctx.froms
+    def compile_update(values, key = nil)
+      um = UpdateManager.new(source)
+      um.set(values)
+      um.take(limit)
+      um.offset(offset)
+      um.order(*orders)
+      um.wheres = constraints
+      um.key = key
+      um
+    end
+
+    def compile_delete(key = nil)
+      dm = DeleteManager.new(source)
+      dm.take(limit)
+      dm.offset(offset)
+      dm.order(*orders)
+      dm.wheres = constraints
+      dm.key = key
       dm
     end
   end