Source code for openlp.core.common.db

# -*- coding: utf-8 -*-
# vim: autoindent shiftwidth=4 expandtab textwidth=120 tabstop=4 softtabstop=4

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# OpenLP - Open Source Lyrics Projection                                      #
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"""
The :mod:`db` module provides helper functions for database related methods.
"""
import logging
from copy import deepcopy

import sqlalchemy


log = logging.getLogger(__name__)


[docs]def drop_column(op, tablename, columnname): drop_columns(op, tablename, [columnname])
[docs]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)