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# -*- coding: utf-8 -*-
# vim: autoindent shiftwidth=4 expandtab textwidth=120 tabstop=4 softtabstop=4
###############################################################################
# OpenLP - Open Source Lyrics Projection #
# --------------------------------------------------------------------------- #
# Copyright (c) 2008-2019 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
from copy import deepcopy
import sqlalchemy
log = logging.getLogger(__name__)
def drop_column(op, tablename, columnname):
drop_columns(op, tablename, [columnname])
def drop_columns(op, tablename, columns):
"""
Column dropping functionality for SQLite, as there is no DROP COLUMN support in SQLite
From https://github.com/klugjohannes/alembic-sqlite
"""
# 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 = [deepcopy(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)
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