Domain type

Added a new Postgresql :class:`_postgresql.DOMAIN` datatype, which follows
the same CREATE TYPE / DROP TYPE behaviors as that of PostgreSQL
:class:`_postgresql.ENUM`. Much thanks to David Baumgold for the efforts on
this.

Fixes: #7316
Closes: #7317
Pull-request: https://github.com/sqlalchemy/sqlalchemy/pull/7317
Pull-request-sha: bc9a82f010e6ca2f70a6e8a7620b748e483c26c3

Change-Id: Id8d7e48843a896de17d20cc466b115b3cc065132

1 files changed, 9 insertions, 8 deletions

diff --git a/lib/sqlalchemy/sql/compiler.py b/lib/sqlalchemy/sql/compiler.py
index 8ce0c65e4..1ad547b79 100644
--- a/lib/sqlalchemy/sql/compiler.py
+++ b/lib/sqlalchemy/sql/compiler.py
@@ -5251,17 +5251,18 @@ class DDLCompiler(Compiled):
 
     def get_column_default_string(self, column):
         if isinstance(column.server_default, schema.DefaultClause):
-            if isinstance(column.server_default.arg, str):
-                return self.sql_compiler.render_literal_value(
-                    column.server_default.arg, sqltypes.STRINGTYPE
-                )
-            else:
-                return self.sql_compiler.process(
-                    column.server_default.arg, literal_binds=True
-                )
+            return self.render_default_string(column.server_default.arg)
         else:
             return None
 
+    def render_default_string(self, default):
+        if isinstance(default, str):
+            return self.sql_compiler.render_literal_value(
+                default, sqltypes.STRINGTYPE
+            )
+        else:
+            return self.sql_compiler.process(default, literal_binds=True)
+
     def visit_table_or_column_check_constraint(self, constraint, **kw):
         if constraint.is_column_level:
             return self.visit_column_check_constraint(constraint)