I made some changes in this commit to help out with other people trying to work

around the SQLite problems with Alter table. I added a new function to
migration_tools (replace_table) which does all the work I did in my migration of
core__users, but is now usable for other migrations.

mediagoblin/db/migration_tools.py

@@ -16,6 +16,7 @@
 
 from mediagoblin.tools.common import simple_printer
 from sqlalchemy import Table
+from sqlalchemy.sql import select
 
 class TableAlreadyExists(Exception):
     pass
@@ -286,3 +287,29 @@ def inspect_table(metadata, table_name):
     """Simple helper to get a ref to an already existing table"""
     return Table(table_name, metadata, autoload=True,
                  autoload_with=metadata.bind)
+
+def replace_table(db, old_table,replacement_table):
+    """A function to fully replace a current table with a new one for migrati-
+    -ons. This is necessary because some changes are made tricky in some situa-
+    -tion, for example, dropping a boolean column in sqlite is impossible w/o
+    this method
+
+        :param old_table            A ref to the old table, gotten through 
+                                    inspect_table
+
+        :param replacement_table    A ref to the new table, gotten through
+                                    inspect_table"""
+    surviving_columns = replacement_table.columns.keys()
+    old_table_name = old_table.name
+    for row in db.execute(select(
+        [column for column in old_table.columns
+            if column.name in surviving_columns])):
+
+        db.execute(replacement_table.insert().values(**row))
+    db.commit()
+
+    old_table.drop()
+    db.commit()
+
+    replacement_table.name=old_table_name
+    db.commit()

mediagoblin/db/migrations.py

@@ -27,7 +27,8 @@ from migrate.changeset.constraint import UniqueConstraint
 
 
 from mediagoblin.db.extratypes import JSONEncoded, MutationDict
-from mediagoblin.db.migration_tools import RegisterMigration, inspect_table
+from mediagoblin.db.migration_tools import (RegisterMigration, inspect_table,
+        replace_table)
 from mediagoblin.db.models import (MediaEntry, Collection, MediaComment, User, 
         Privilege)
 
@@ -683,7 +684,7 @@ def create_moderation_tables(db):
 
     db.commit()
 
-    # And then, once the information is taken from the is_admin & status columns
+    # And then, once the information is taken from is_admin & status columns
     # we drop all of the vestigial columns from the User table.
     #--------------------------------------------------------------------------
     if db.bind.url.drivername == 'sqlite':
@@ -694,25 +695,7 @@ def create_moderation_tables(db):
         User_vR1.__table__.create(db.bind)
         db.commit()
         new_user_table = inspect_table(metadata, 'rename__users')
-        for row in db.execute(user_table.select()):
-            db.execute(new_user_table.insert().values(
-                username=row.username,
-                email=row.email,
-                pw_hash=row.pw_hash,
-                created=row.created,
-                wants_comment_notification=row.wants_comment_notification,
-                wants_notifications=row.wants_notifications,
-                license_preference=row.license_preference,
-                url=row.url,
-                bio=row.bio,
-                uploaded=row.uploaded,
-                upload_limit=row.upload_limit))
-
-        db.commit()
-        user_table.drop()
-
-        db.commit()
-        new_user_table.rename("core__users")
+        replace_table(db,user_table, new_user_table)
     else:
         # If the db is not run using SQLite, this process is much simpler ~~~~~