Revision

The RevisionMap object serves as the basis for revisionmanagement, used exclusively by ScriptDirectory .

  • exception alembic.script.revision. CycleDetected (revisions: Sequence[str])

  • exception alembic.script.revision. DependencyCycleDetected (revisions: Sequence[str])

  • exception alembic.script.revision. DependencyLoopDetected (revision: Sequence[str])

  • exception alembic.script.revision. LoopDetected (revision: str)

  • exception alembic.script.revision. MultipleHeads (heads: Sequence[str], argument: Optional[str])

  • exception alembic.script.revision. RangeNotAncestorError (lower: Optional[Union[str, Tuple[str, ...]]], upper: Optional[Union[str, Tuple[str, ...]]])

  • exception alembic.script.revision. ResolutionError (message: str, argument: str)

  • class alembic.script.revision. Revision (revision: str, down_revision: Optional[Union[str, Tuple[str, ...]]], dependencies: Optional[Tuple[str, ...]] = None, branch_labels: Optional[Tuple[str, ...]] = None)

    Base class for revisioned objects.

    The Revision class is the base of the more public-facing Script object, which represents a migration script.The mechanics of revision management and traversal are encapsulatedwithin Revision , while Script applies this logicto Python files in a version directory.

    • branch_labels : Set[str] = None

      Optional string/tuple of symbolic names to apply to thisrevision"™s branch

    • dependencies : Optional[Union[str, Sequence[str]]] = None

      Additional revisions which this revision is dependent on.

      From a migration standpoint, these dependencies are added to thedown_revision to form the full iteration. However, the separationof down_revision from “dependencies” is to assist in navigatinga history that contains many branches, typically a multi-root scenario.

    • down_revision : Optional[Union[str, Sequence[str]]] = None

      The down_revision identifier(s) within the migration script.

      Note that the total set of "down" revisions isdown_revision + dependencies.

    • property is_base : bool

      Return True if this Revision is a "base"™ revision.

    • property is_branch_point : bool

      Return True if this Script is a branch point.

      A branchpoint is defined as a Script which is referredto by more than one succeeding Script , that is morethan one Script has a identifier pointinghere.

    • property is_head : bool

      Return True if this Revision is a "head"™ revision.

      This is determined based on whether any other Script within the ScriptDirectory refers to this Script . Multiple heads can be present.

    • property is_merge_point : bool

      Return True if this Script is a merge point.

    • nextrev : FrozenSet[str] = frozenset({})

      following revisions, based on down_revision only.

    • revision : str = None

      The string revision number.

  • exception alembic.script.revision. RevisionError

  • class alembic.script.revision. RevisionMap (generator: Callable[[], Iterator[alembic.script.revision.Revision]])

    Maintains a map of Revision objects.

    RevisionMap is used by ScriptDirectory to maintainand traverse the collection of Script objects, which arethemselves instances of Revision .

    Construct a new RevisionMap .

    Parameters:

    • generator "“ a zero-arg callable that will generate an iterableof Revision instances to be used. These are typically Script subclasses within regular Alembic use.

    • add_revision (revision: alembic.script.revision.Revision, _replace: bool = False) → None

      add a single revision to an existing map.

      This method is for single-revision use cases, it"™s notappropriate for fully populating an entire revision map.

    • bases

      All ”base“ revisions as strings.

      These are revisions that have a down_revision of None,or empty tuple.

      Returns：

      • a tuple of string revision numbers.

    • get_current_head (branch_label: Optional[str] = None) → Optional[str]

      Return the current head revision.

      If the script directory has multiple headsdue to branching, an error is raised; ScriptDirectory.get_heads() should bepreferred.

      Parameters:

      • branch_label "“ optional branch name which will limit theheads considered to those which include that branch_label.

      Returns: a string revision number.

      See also: ScriptDirectory.get_heads()

    • get_revision (id_: Optional[str]) → alembic.script.revision.Revision

      Return the Revision instance with the given rev id.

      If a symbolic name such as "head" or "base" is given, resolvesthe identifier into the current head or base revision. If the symbolicname refers to multiples, MultipleHeads is raised.

      Supports partial identifiers, where the given identifieris matched against all identifiers that start with the givencharacters; if there is exactly one match, that determines thefull revision.

    • get_revisions (id_: Optional[Union[str, Collection[str]]]) → Tuple[alembic.script.revision.Revision, ...]

      Return the Revision instances with the given rev idor identifiers.

      May be given a single identifier, a sequence of identifiers, or thespecial symbols "head" or "base". The result is a tuple of oneor more identifiers, or an empty tuple in the case of "base".

      In the cases where "head"™, "heads"™ is requested and therevision map is empty, returns an empty tuple.

      Supports partial identifiers, where the given identifieris matched against all identifiers that start with the givencharacters; if there is exactly one match, that determines thefull revision.

    • heads

      All "head" revisions as strings.

      This is normally a tuple of length one,unless unmerged branches are present.

      Returns: a tuple of string revision numbers.

    • iterate_revisions (upper: Optional[Union[str, Tuple[str, ...]]], lower: Optional[Union[str, Tuple[str, ...]]], implicit_base: bool = False, inclusive: bool = False, assert_relative_length: bool = True, select_for_downgrade: bool = False) → Iterator[alembic.script.revision.Revision]

      Iterate through script revisions, starting at the givenupper revision identifier and ending at the lower.

      The traversal uses strictly the marker inside each migration script, soit is a requirement that upper >= lower,else you"™ll get nothing back.

      The iterator yields Revision objects.