diff options
Diffstat (limited to 'django')
| -rw-r--r-- | django/db/migrations/migration.py | 6 | ||||
| -rw-r--r-- | django/db/migrations/operations/__init__.py | 2 | ||||
| -rw-r--r-- | django/db/migrations/operations/base.py | 3 | ||||
| -rw-r--r-- | django/db/migrations/operations/special.py | 42 |
4 files changed, 51 insertions, 2 deletions
diff --git a/django/db/migrations/migration.py b/django/db/migrations/migration.py index 277c5faa3f..f65b6b2d0c 100644 --- a/django/db/migrations/migration.py +++ b/django/db/migrations/migration.py @@ -32,6 +32,10 @@ class Migration(object): # are not applied. replaces = [] + # Error class which is raised when a migration is irreversible + class IrreversibleError(RuntimeError): + pass + def __init__(self, name, app_label): self.name = name self.app_label = app_label @@ -91,6 +95,8 @@ class Migration(object): # We need to pre-calculate the stack of project states to_run = [] for operation in self.operations: + if not operation.reversible: + raise Migration.IrreversibleError("Operation %s in %s is not reversible" % (operation, sekf)) new_state = project_state.clone() operation.state_forwards(self.app_label, new_state) to_run.append((operation, project_state, new_state)) diff --git a/django/db/migrations/operations/__init__.py b/django/db/migrations/operations/__init__.py index f59dda9b00..de91961298 100644 --- a/django/db/migrations/operations/__init__.py +++ b/django/db/migrations/operations/__init__.py @@ -1,3 +1,3 @@ from .models import CreateModel, DeleteModel, AlterModelTable, AlterUniqueTogether, AlterIndexTogether from .fields import AddField, RemoveField, AlterField, RenameField -from .special import SeparateDatabaseAndState, RunSQL +from .special import SeparateDatabaseAndState, RunSQL, RunPython diff --git a/django/db/migrations/operations/base.py b/django/db/migrations/operations/base.py index 217c6ee843..1e5789f29c 100644 --- a/django/db/migrations/operations/base.py +++ b/django/db/migrations/operations/base.py @@ -15,6 +15,9 @@ class Operation(object): # Some operations are impossible to reverse, like deleting data. reversible = True + # Can this migration be represented as SQL? (things like RunPython cannot) + reduces_to_sql = True + def __new__(cls, *args, **kwargs): # We capture the arguments to make returning them trivial self = object.__new__(cls) diff --git a/django/db/migrations/operations/special.py b/django/db/migrations/operations/special.py index 886c012273..7bd4ac2117 100644 --- a/django/db/migrations/operations/special.py +++ b/django/db/migrations/operations/special.py @@ -1,5 +1,5 @@ import re - +import textwrap from .base import Operation @@ -59,6 +59,10 @@ class RunSQL(Operation): self.state_operations = state_operations or [] self.multiple = multiple + @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) @@ -92,3 +96,39 @@ class RunSQL(Operation): def describe(self): return "Raw SQL operation" + + +class RunPython(Operation): + """ + Runs Python code in a context suitable for doing versioned ORM operations. + """ + + reduces_to_sql = False + reversible = False + + def __init__(self, code): + # Trim any leading whitespace that is at the start of all code lines + # so users can nicely indent code in migration files + code = textwrap.dedent(code) + # Run the code through a parser first to make sure it's at least + # syntactically correct + self.code = compile(code, "<string>", "exec") + + 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): + # We now execute the Python code in a context that contains a 'models' + # object, representing the versioned models as an AppCache. + # We could try to override the global cache, but then people will still + # use direct imports, so we go with a documentation approach instead. + context = { + "models": from_state.render(), + "schema_editor": schema_editor, + } + eval(self.code, context) + + def database_backwards(self, app_label, schema_editor, from_state, to_state): + raise NotImplementedError("You cannot reverse this operation") |