Source code for django.db.migrations.operations.special
from django.db import router
from .base import Operation
[docs]
class SeparateDatabaseAndState(Operation):
"""
Take two lists of operations - ones that will be used for the database,
and ones that will be used for the state change. This allows operations
that don't support state change to have it applied, or have operations
that affect the state or not the database, or so on.
"""
serialization_expand_args = ["database_operations", "state_operations"]
def __init__(self, database_operations=None, state_operations=None):
self.database_operations = database_operations or []
self.state_operations = state_operations or []
def deconstruct(self):
kwargs = {}
if self.database_operations:
kwargs["database_operations"] = self.database_operations
if self.state_operations:
kwargs["state_operations"] = self.state_operations
return (self.__class__.__qualname__, [], kwargs)
def state_forwards(self, app_label, state):
for state_operation in self.state_operations:
state_operation.state_forwards(app_label, state)
def database_forwards(self, app_label, schema_editor, from_state, to_state):
# We calculate state separately in here since our state functions aren't useful
for database_operation in self.database_operations:
to_state = from_state.clone()
database_operation.state_forwards(app_label, to_state)
database_operation.database_forwards(
app_label, schema_editor, from_state, to_state
)
from_state = to_state
def database_backwards(self, app_label, schema_editor, from_state, to_state):
# We calculate state separately in here since our state functions aren't useful
to_states = {}
for dbop in self.database_operations:
to_states[dbop] = to_state
to_state = to_state.clone()
dbop.state_forwards(app_label, to_state)
# to_state now has the states of all the database_operations applied
# which is the from_state for the backwards migration of the last
# operation.
for database_operation in reversed(self.database_operations):
from_state = to_state
to_state = to_states[database_operation]
database_operation.database_backwards(
app_label, schema_editor, from_state, to_state
)
def describe(self):
return "Custom state/database change combination"
[docs]
class RunSQL(Operation):
"""
Run some raw SQL. A reverse SQL statement may be provided.
Also accept a list of operations that represent the state change effected
by this SQL change, in case it's custom column/table creation/deletion.
"""
noop = ""
def __init__(
self, sql, reverse_sql=None, state_operations=None, hints=None, elidable=False
):
self.sql = sql
self.reverse_sql = reverse_sql
self.state_operations = state_operations or []
self.hints = hints or {}
self.elidable = elidable
def deconstruct(self):
kwargs = {
"sql": self.sql,
}
if self.reverse_sql is not None:
kwargs["reverse_sql"] = self.reverse_sql
if self.state_operations:
kwargs["state_operations"] = self.state_operations
if self.hints:
kwargs["hints"] = self.hints
return (self.__class__.__qualname__, [], kwargs)
@property
def reversible(self):
return self.reverse_sql is not None
def state_forwards(self, app_label, state):
for state_operation in self.state_operations:
state_operation.state_forwards(app_label, state)
def database_forwards(self, app_label, schema_editor, from_state, to_state):
if router.allow_migrate(
schema_editor.connection.alias, app_label, **self.hints
):
self._run_sql(schema_editor, self.sql)
def database_backwards(self, app_label, schema_editor, from_state, to_state):
if self.reverse_sql is None:
raise NotImplementedError("You cannot reverse this operation")
if router.allow_migrate(
schema_editor.connection.alias, app_label, **self.hints
):
self._run_sql(schema_editor, self.reverse_sql)
def describe(self):
return "Raw SQL operation"
def _run_sql(self, schema_editor, sqls):
if isinstance(sqls, (list, tuple)):
for sql in sqls:
params = None
if isinstance(sql, (list, tuple)):
elements = len(sql)
if elements == 2:
sql, params = sql
else:
raise ValueError("Expected a 2-tuple but got %d" % elements)
schema_editor.execute(sql, params=params)
elif sqls != RunSQL.noop:
statements = schema_editor.connection.ops.prepare_sql_script(sqls)
for statement in statements:
schema_editor.execute(statement, params=None)
[docs]
class RunPython(Operation):
"""
Run Python code in a context suitable for doing versioned ORM operations.
"""
reduces_to_sql = False
def __init__(
self, code, reverse_code=None, atomic=None, hints=None, elidable=False
):
self.atomic = atomic
# Forwards code
if not callable(code):
raise ValueError("RunPython must be supplied with a callable")
self.code = code
# Reverse code
if reverse_code is None:
self.reverse_code = None
else:
if not callable(reverse_code):
raise ValueError("RunPython must be supplied with callable arguments")
self.reverse_code = reverse_code
self.hints = hints or {}
self.elidable = elidable
def deconstruct(self):
kwargs = {
"code": self.code,
}
if self.reverse_code is not None:
kwargs["reverse_code"] = self.reverse_code
if self.atomic is not None:
kwargs["atomic"] = self.atomic
if self.hints:
kwargs["hints"] = self.hints
return (self.__class__.__qualname__, [], kwargs)
@property
def reversible(self):
return self.reverse_code is not None
def state_forwards(self, app_label, state):
# RunPython objects have no state effect. To add some, combine this
# with SeparateDatabaseAndState.
pass
def database_forwards(self, app_label, schema_editor, from_state, to_state):
# RunPython has access to all models. Ensure that all models are
# reloaded in case any are delayed.
from_state.clear_delayed_apps_cache()
if router.allow_migrate(
schema_editor.connection.alias, app_label, **self.hints
):
# We now execute the Python code in a context that contains a 'models'
# object, representing the versioned models as an app registry.
# We could try to override the global cache, but then people will still
# use direct imports, so we go with a documentation approach instead.
self.code(from_state.apps, schema_editor)
def database_backwards(self, app_label, schema_editor, from_state, to_state):
if self.reverse_code is None:
raise NotImplementedError("You cannot reverse this operation")
if router.allow_migrate(
schema_editor.connection.alias, app_label, **self.hints
):
self.reverse_code(from_state.apps, schema_editor)
def describe(self):
return "Raw Python operation"
