1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
|
# 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 contextlib
import functools
from alembic import context
from alembic import op
import sqlalchemy as sa
from sqlalchemy.engine import reflection
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})
def remove_foreign_keys(table, foreign_keys):
for fk in foreign_keys:
op.drop_constraint(
name=fk['name'],
table_name=table,
type_='foreignkey'
)
def create_foreign_keys(table, foreign_keys):
for fk in foreign_keys:
op.create_foreign_key(
name=fk['name'],
source=table,
referent=fk['referred_table'],
local_cols=fk['constrained_columns'],
remote_cols=fk['referred_columns'],
ondelete='CASCADE'
)
@contextlib.contextmanager
def remove_fks_from_table(table):
try:
inspector = reflection.Inspector.from_engine(op.get_bind())
foreign_keys = inspector.get_foreign_keys(table)
remove_foreign_keys(table, foreign_keys)
yield
finally:
create_foreign_keys(table, foreign_keys)
|
