pg uses DROP NOT NULL, keep this as the default and move

NULL to SQL Server, until we get more data on other DBs

2 files changed, 10 insertions, 2 deletions

diff --git a/alembic/ddl/base.py b/alembic/ddl/base.py
index 58e3006..5fb5d9c 100644
--- a/alembic/ddl/base.py
+++ b/alembic/ddl/base.py
@@ -80,7 +80,7 @@ def visit_column_nullable(element, compiler, **kw):
     return "%s %s %s" % (
         alter_table(compiler, element.table_name, element.schema),
         alter_column(compiler, element.column_name),
-        "NULL" if element.nullable else "SET NOT NULL"
+        "DROP NOT NULL" if element.nullable else "SET NOT NULL"
     )
 
 @compiles(ColumnType)
diff --git a/alembic/ddl/mssql.py b/alembic/ddl/mssql.py
index 42c2952..3f2b45b 100644
--- a/alembic/ddl/mssql.py
+++ b/alembic/ddl/mssql.py
@@ -1,5 +1,5 @@
 from alembic.ddl.impl import DefaultImpl
-from alembic.ddl.base import alter_table, AddColumn, ColumnName, format_table_name, format_column_name
+from alembic.ddl.base import alter_table, AddColumn, ColumnName, format_table_name, format_column_name, ColumnNullable, alter_column
 from sqlalchemy.ext.compiler import compiles
 
 class MSSQLImpl(DefaultImpl):
@@ -59,6 +59,14 @@ def visit_add_column(element, compiler, **kw):
 def mssql_add_column(compiler, column, **kw):
     return "ADD %s" % compiler.get_column_specification(column, **kw)
 
+@compiles(ColumnNullable, 'mssql')
+def visit_column_nullable(element, compiler, **kw):
+    return "%s %s %s" % (
+        alter_table(compiler, element.table_name, element.schema),
+        alter_column(compiler, element.column_name),
+        "NULL" if element.nullable else "SET NOT NULL"
+    )
+
 
 @compiles(ColumnName, 'mssql')
 def visit_rename_column(element, compiler, **kw):