Add missing file

openlp/core/utils/db.py

@@ -0,0 +1,73 @@
+# -*- coding: utf-8 -*-
+# vim: autoindent shiftwidth=4 expandtab textwidth=120 tabstop=4 softtabstop=4
+
+###############################################################################
+# OpenLP - Open Source Lyrics Projection                                      #
+# --------------------------------------------------------------------------- #
+# Copyright (c) 2008-2016 OpenLP Developers                                   #
+# --------------------------------------------------------------------------- #
+# This program is free software; you can redistribute it and/or modify it     #
+# under the terms of the GNU General Public License as published by the Free  #
+# Software Foundation; version 2 of the License.                              #
+#                                                                             #
+# This program is distributed in the hope that it will be useful, but WITHOUT #
+# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or       #
+# FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for    #
+# more details.                                                               #
+#                                                                             #
+# You should have received a copy of the GNU General Public License along     #
+# with this program; if not, write to the Free Software Foundation, Inc., 59  #
+# Temple Place, Suite 330, Boston, MA 02111-1307 USA                          #
+###############################################################################
+"""
+The :mod:`db` module provides helper functions for database related methods.
+"""
+import logging
+
+log = logging.getLogger(__name__)
+
+import sqlalchemy
+
+
+def drop_columns(op, tablename, columns):
+    """
+    Column dropping functionality for SQLite, as there is no native support, neither in Alembic, nor in SQLite
+
+    From https://github.com/klugjohannes/alembic-sqlite
+    """
+
+    # we need copy to make a deep copy of the column attributes
+    from copy import copy
+
+    # get the db engine and reflect database tables
+    engine = op.get_bind()
+    meta = sqlalchemy.MetaData(bind=engine)
+    meta.reflect()
+
+    # create a select statement from the old table
+    old_table = meta.tables[tablename]
+    select = sqlalchemy.sql.select([c for c in old_table.c if c.name not in columns])
+
+    # get remaining columns without table attribute attached
+    remaining_columns = [copy(c) for c in old_table.columns if c.name not in columns]
+    for column in remaining_columns:
+        column.table = None
+
+    # create a temporary new table
+    new_tablename = '{0}_new'.format(tablename)
+    op.create_table(new_tablename, *remaining_columns)
+    meta.reflect()
+    new_table = meta.tables[new_tablename]
+
+    # copy data from old table
+    insert = sqlalchemy.sql.insert(new_table).from_select([c.name for c in remaining_columns], select)
+    engine.execute(insert)
+
+    # drop the old table and rename the new table to take the old tables
+    # position
+    op.drop_table(tablename)
+    op.rename_table(new_tablename, tablename)
+
+
+def drop_column(tablename, columnname):
+    drop_column(tablename, [columnname])