- Some deep-in-the-weeds fixes to try to get "server default" comparison

working better across platforms and expressions, in particular on
the Postgresql backend, mostly dealing with quoting/not quoting of various
expressions at the appropriate time and on a per-backend basis.
Repaired and tested support for such defaults as Postgresql interval
and array defaults.
fixes #212

2 files changed, 15 insertions, 3 deletions

diff --git a/alembic/ddl/postgresql.py b/alembic/ddl/postgresql.py
index 5ca0d1f..27f31b0 100644
--- a/alembic/ddl/postgresql.py
+++ b/alembic/ddl/postgresql.py
@@ -1,7 +1,7 @@
 import re
 
 from sqlalchemy import types as sqltypes
-
+from .. import compat
 from .base import compiles, alter_table, format_table_name, RenameTable
 from .impl import DefaultImpl
 
@@ -24,8 +24,11 @@ class PostgresqlImpl(DefaultImpl):
         if None in (conn_col_default, rendered_metadata_default):
             return conn_col_default != rendered_metadata_default
 
-        if metadata_column.type._type_affinity is not sqltypes.String:
-            rendered_metadata_default = re.sub(r"^'|'$", "", rendered_metadata_default)
+        if metadata_column.server_default is not None and \
+            isinstance(metadata_column.server_default.arg,
+                        compat.string_types) and \
+                not re.match(r"^'.+'$", rendered_metadata_default):
+            rendered_metadata_default = "'%s'" % rendered_metadata_default
 
         return not self.connection.scalar(
             "SELECT %s = %s" % (
diff --git a/alembic/ddl/sqlite.py b/alembic/ddl/sqlite.py
index a3c73ce..85c829e 100644
--- a/alembic/ddl/sqlite.py
+++ b/alembic/ddl/sqlite.py
@@ -1,5 +1,6 @@
 from .. import util
 from .impl import DefaultImpl
+import re
 
 #from sqlalchemy.ext.compiler import compiles
 #from .base import AddColumn, alter_table
@@ -29,6 +30,14 @@ class SQLiteImpl(DefaultImpl):
             raise NotImplementedError(
                     "No support for ALTER of constraints in SQLite dialect")
 
+    def compare_server_default(self, inspector_column,
+                            metadata_column,
+                            rendered_metadata_default,
+                            rendered_inspector_default):
+
+        rendered_metadata_default = re.sub(r"^'|'$", "", rendered_metadata_default)
+        return rendered_inspector_default != repr(rendered_metadata_default)
+
     def correct_for_autogen_constraints(self, conn_unique_constraints, conn_indexes,
                                         metadata_unique_constraints,
                                         metadata_indexes):