1 files changed, 35 insertions, 0 deletions
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/schema_creation.rb b/activerecord/lib/active_record/connection_adapters/abstract/schema_creation.rb
index 47fe501752..adad6cd542 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/schema_creation.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/schema_creation.rb
@@ -23,6 +23,8 @@ module ActiveRecord
           def visit_AlterTable(o)
             sql = "ALTER TABLE #{quote_table_name(o.name)} "
             sql << o.adds.map { |col| visit_AddColumn col }.join(' ')
+            sql << o.foreign_key_adds.map { |fk| visit_AddForeignKey fk }.join(' ')
+            sql << o.foreign_key_drops.map { |fk| visit_DropForeignKey fk }.join(' ')
           end
 
           def visit_ColumnDefinition(o)
@@ -41,6 +43,21 @@ module ActiveRecord
             create_sql
           end
 
+          def visit_AddForeignKey(o)
+            sql = <<-SQL.strip_heredoc
+              ADD CONSTRAINT #{quote_column_name(o.name)}
+              FOREIGN KEY (#{quote_column_name(o.column)})
+                REFERENCES #{quote_table_name(o.to_table)} (#{quote_column_name(o.primary_key)})
+            SQL
+            sql << " #{action_sql('DELETE', o.on_delete)}" if o.on_delete
+            sql << " #{action_sql('UPDATE', o.on_update)}" if o.on_update
+            sql
+          end
+
+          def visit_DropForeignKey(name)
+            "DROP CONSTRAINT #{quote_column_name(name)}"
+          end
+
           def column_options(o)
             column_options = {}
             column_options[:null] = o.null unless o.null.nil?
@@ -77,6 +94,7 @@ module ActiveRecord
 
           def quote_value(value, column)
             column.sql_type ||= type_to_sql(column.type, column.limit, column.precision, column.scale)
+            column.cast_type ||= type_for_column(column)
 
             @conn.quote(value, column)
           end
@@ -84,6 +102,23 @@ module ActiveRecord
           def options_include_default?(options)
             options.include?(:default) && !(options[:null] == false && options[:default].nil?)
           end
+
+          def action_sql(action, dependency)
+            case dependency
+            when :nullify then "ON #{action} SET NULL"
+            when :cascade  then "ON #{action} CASCADE"
+            when :restrict then "ON #{action} RESTRICT"
+            else
+              raise ArgumentError, <<-MSG.strip_heredoc
+                '#{dependency}' is not supported for :on_update or :on_delete.
+                Supported values are: :nullify, :cascade, :restrict
+              MSG
+            end
+          end
+
+          def type_for_column(column)
+            @conn.lookup_cast_type(column.sql_type)
+          end
       end
     end
   end