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# Copyright 2014 Mirantis Inc.
# Copyright 2014 OpenStack Foundation
#
# Licensed under the Apache License, Version 2.0 (the "License"); you may
# not use this file except in compliance with the License. You may obtain
# a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations
# under the License.
import six
import uuid
from alembic import op
import sqlalchemy
def sqlite_alter_columns(table_name, column_defs):
"""Implement alter columns for SQLite.
The ALTER COLUMN command isn't supported by SQLite specification.
Instead of calling ALTER COLUMN it uses the following workaround:
* create temp table '{table_name}_{rand_uuid}', with some column
defs replaced;
* copy all data to the temp table;
* drop old table;
* rename temp table to the old table name.
"""
connection = op.get_bind()
meta = sqlalchemy.MetaData(bind=connection)
meta.reflect()
changed_columns = {}
indexes = []
for col in column_defs:
# If we are to have an index on the column, don't create it
# immediately, instead, add it to a list of indexes to create
# after the table rename.
if col.index:
indexes.append(('ix_%s_%s' % (table_name, col.name),
table_name,
[col.name],
col.unique))
col.unique = False
col.index = False
changed_columns[col.name] = col
# construct lists of all columns and their names
old_columns = []
new_columns = []
column_names = []
for column in meta.tables[table_name].columns:
column_names.append(column.name)
old_columns.append(column)
if column.name in changed_columns.keys():
new_columns.append(changed_columns[column.name])
else:
col_copy = column.copy()
new_columns.append(col_copy)
for key in meta.tables[table_name].foreign_keys:
constraint = key.constraint
con_copy = constraint.copy()
new_columns.append(con_copy)
for index in meta.tables[table_name].indexes:
# If this is a single column index for a changed column, don't
# copy it because we may already be creating a new version of
# it (or removing it).
idx_columns = [col.name for col in index.columns]
if len(idx_columns)==1 and idx_columns[0] in changed_columns.keys():
continue
# Otherwise, recreate the index.
indexes.append((index.name,
table_name,
[col.name for col in index.columns],
index.unique))
# create temp table
tmp_table_name = "%s_%s" % (table_name, six.text_type(uuid.uuid4()))
op.create_table(tmp_table_name, *new_columns)
meta.reflect()
try:
# copy data from the old table to the temp one
sql_select = sqlalchemy.sql.select(old_columns)
connection.execute(sqlalchemy.sql.insert(meta.tables[tmp_table_name])
.from_select(column_names, sql_select))
except Exception:
op.drop_table(tmp_table_name)
raise
# drop the old table and rename temp table to the old table name
op.drop_table(table_name)
op.rename_table(tmp_table_name, table_name)
# (re-)create indexes
for index in indexes:
op.create_index(op.f(index[0]), index[1], index[2], unique=index[3])
def sqlite_drop_columns(table_name, drop_columns):
"""Implement drop columns for SQLite.
The DROP COLUMN command isn't supported by SQLite specification.
Instead of calling DROP COLUMN it uses the following workaround:
* create temp table '{table_name}_{rand_uuid}', without
dropped columns;
* copy all data to the temp table;
* drop old table;
* rename temp table to the old table name.
"""
connection = op.get_bind()
meta = sqlalchemy.MetaData(bind=connection)
meta.reflect()
# construct lists of all columns and their names
old_columns = []
new_columns = []
column_names = []
indexes = []
for column in meta.tables[table_name].columns:
if column.name not in drop_columns:
old_columns.append(column)
column_names.append(column.name)
col_copy = column.copy()
new_columns.append(col_copy)
for key in meta.tables[table_name].foreign_keys:
# If this is a single column constraint for a dropped column,
# don't copy it.
columns = [c.name for c in key.constraint.columns]
if (len(columns)==1 and columns[0] in drop_columns):
continue
# Otherwise, recreate the constraint.
constraint = key.constraint
con_copy = constraint.copy()
new_columns.append(con_copy)
for index in meta.tables[table_name].indexes:
# If this is a single column index for a dropped column, don't
# copy it.
idx_columns = [col.name for col in index.columns]
if len(idx_columns)==1 and idx_columns[0] in drop_columns:
continue
# Otherwise, recreate the index.
indexes.append((index.name,
table_name,
[col.name for col in index.columns],
index.unique))
# create temp table
tmp_table_name = "%s_%s" % (table_name, six.text_type(uuid.uuid4()))
op.create_table(tmp_table_name, *new_columns)
meta.reflect()
try:
# copy data from the old table to the temp one
sql_select = sqlalchemy.sql.select(old_columns)
connection.execute(sqlalchemy.sql.insert(meta.tables[tmp_table_name])
.from_select(column_names, sql_select))
except Exception:
op.drop_table(tmp_table_name)
raise
# drop the old table and rename temp table to the old table name
op.drop_table(table_name)
op.rename_table(tmp_table_name, table_name)
# (re-)create indexes
for index in indexes:
op.create_index(op.f(index[0]), index[1], index[2], unique=index[3])