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# Copyright 2012 New Dream Network, LLC (DreamHost)
#
# 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 functools
from alembic import context
from alembic import op
import sqlalchemy as sa
def skip_if_offline(func):
"""Decorator for skipping migrations in offline mode."""
@functools.wraps(func)
def decorator(*args, **kwargs):
if context.is_offline_mode():
return
return func(*args, **kwargs)
return decorator
def raise_if_offline(func):
"""Decorator for raising if a function is called in offline mode."""
@functools.wraps(func)
def decorator(*args, **kwargs):
if context.is_offline_mode():
raise RuntimeError(_("%s cannot be called while in offline mode") %
func.__name__)
return func(*args, **kwargs)
return decorator
@raise_if_offline
def schema_has_table(table_name):
"""Check whether the specified table exists in the current schema.
This method cannot be executed in offline mode.
"""
bind = op.get_bind()
insp = sa.engine.reflection.Inspector.from_engine(bind)
return table_name in insp.get_table_names()
@raise_if_offline
def schema_has_column(table_name, column_name):
"""Check whether the specified column exists in the current schema.
This method cannot be executed in offline mode.
"""
bind = op.get_bind()
insp = sa.engine.reflection.Inspector.from_engine(bind)
# first check that the table exists
if not schema_has_table(table_name):
return
# check whether column_name exists in table columns
return column_name in [column['name'] for column in
insp.get_columns(table_name)]
@raise_if_offline
def alter_column_if_exists(table_name, column_name, **kwargs):
"""Alter a column only if it exists in the schema."""
if schema_has_column(table_name, column_name):
op.alter_column(table_name, column_name, **kwargs)
@raise_if_offline
def drop_table_if_exists(table_name):
if schema_has_table(table_name):
op.drop_table(table_name)
@raise_if_offline
def rename_table_if_exists(old_table_name, new_table_name):
if schema_has_table(old_table_name):
op.rename_table(old_table_name, new_table_name)
def alter_enum(table, column, enum_type, nullable):
bind = op.get_bind()
engine = bind.engine
if engine.name == 'postgresql':
values = {'table': table,
'column': column,
'name': enum_type.name}
op.execute("ALTER TYPE %(name)s RENAME TO old_%(name)s" % values)
enum_type.create(bind, checkfirst=False)
op.execute("ALTER TABLE %(table)s RENAME COLUMN %(column)s TO "
"old_%(column)s" % values)
op.add_column(table, sa.Column(column, enum_type, nullable=nullable))
op.execute("UPDATE %(table)s SET %(column)s = "
"old_%(column)s::text::%(name)s" % values)
op.execute("ALTER TABLE %(table)s DROP COLUMN old_%(column)s" % values)
op.execute("DROP TYPE old_%(name)s" % values)
else:
op.alter_column(table, column, type_=enum_type,
existing_nullable=nullable)
def create_table_if_not_exist_psql(table_name, values):
if op.get_bind().engine.dialect.server_version_info < (9, 1, 0):
op.execute("CREATE LANGUAGE plpgsql")
op.execute("CREATE OR REPLACE FUNCTION execute(TEXT) RETURNS VOID AS $$"
"BEGIN EXECUTE $1; END;"
"$$ LANGUAGE plpgsql STRICT;")
op.execute("CREATE OR REPLACE FUNCTION table_exist(TEXT) RETURNS bool as "
"$$ SELECT exists(select 1 from pg_class where relname=$1);"
"$$ language sql STRICT;")
op.execute("SELECT execute($$CREATE TABLE %(name)s %(columns)s $$) "
"WHERE NOT table_exist(%(name)r);" %
{'name': table_name,
'columns': values})
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