1 files changed, 90 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
new file mode 100644
index 0000000000..47fe501752
--- /dev/null
+++ b/activerecord/lib/active_record/connection_adapters/abstract/schema_creation.rb
@@ -0,0 +1,90 @@
+module ActiveRecord
+  module ConnectionAdapters
+    class AbstractAdapter
+      class SchemaCreation # :nodoc:
+        def initialize(conn)
+          @conn = conn
+          @cache = {}
+        end
+
+        def accept(o)
+          m = @cache[o.class] ||= "visit_#{o.class.name.split('::').last}"
+          send m, o
+        end
+
+        def visit_AddColumn(o)
+          sql_type = type_to_sql(o.type, o.limit, o.precision, o.scale)
+          sql = "ADD #{quote_column_name(o.name)} #{sql_type}"
+          add_column_options!(sql, column_options(o))
+        end
+
+        private
+
+          def visit_AlterTable(o)
+            sql = "ALTER TABLE #{quote_table_name(o.name)} "
+            sql << o.adds.map { |col| visit_AddColumn col }.join(' ')
+          end
+
+          def visit_ColumnDefinition(o)
+            sql_type = type_to_sql(o.type, o.limit, o.precision, o.scale)
+            column_sql = "#{quote_column_name(o.name)} #{sql_type}"
+            add_column_options!(column_sql, column_options(o)) unless o.primary_key?
+            column_sql
+          end
+
+          def visit_TableDefinition(o)
+            create_sql = "CREATE#{' TEMPORARY' if o.temporary} TABLE "
+            create_sql << "#{quote_table_name(o.name)} "
+            create_sql << "(#{o.columns.map { |c| accept c }.join(', ')}) " unless o.as
+            create_sql << "#{o.options}"
+            create_sql << " AS #{@conn.to_sql(o.as)}" if o.as
+            create_sql
+          end
+
+          def column_options(o)
+            column_options = {}
+            column_options[:null] = o.null unless o.null.nil?
+            column_options[:default] = o.default unless o.default.nil?
+            column_options[:column] = o
+            column_options[:first] = o.first
+            column_options[:after] = o.after
+            column_options
+          end
+
+          def quote_column_name(name)
+            @conn.quote_column_name name
+          end
+
+          def quote_table_name(name)
+            @conn.quote_table_name name
+          end
+
+          def type_to_sql(type, limit, precision, scale)
+            @conn.type_to_sql type.to_sym, limit, precision, scale
+          end
+
+          def add_column_options!(sql, options)
+            sql << " DEFAULT #{quote_value(options[:default], options[:column])}" if options_include_default?(options)
+            # must explicitly check for :null to allow change_column to work on migrations
+            if options[:null] == false
+              sql << " NOT NULL"
+            end
+            if options[:auto_increment] == true
+              sql << " AUTO_INCREMENT"
+            end
+            sql
+          end
+
+          def quote_value(value, column)
+            column.sql_type ||= type_to_sql(column.type, column.limit, column.precision, column.scale)
+
+            @conn.quote(value, column)
+          end
+
+          def options_include_default?(options)
+            options.include?(:default) && !(options[:null] == false && options[:default].nil?)
+          end
+      end
+    end
+  end
+end