Class WriteableColumnCollection

lib/sqlalchemy/sql/base.py:2067–2297

A :class:`_sql.ColumnCollection` that allows mutation operations. This is the writable form of :class:`_sql.ColumnCollection` that implements methods such as :meth:`.add`, :meth:`.remove`, :meth:`.update`, and :meth:`.clear`. This class is used internally for building column collec

class WriteableColumnCollection(ColumnCollection[_COLKEY, _COL_co]):
    """A :class:`_sql.ColumnCollection` that allows mutation operations.

    This is the writable form of :class:`_sql.ColumnCollection` that
    implements methods such as :meth:`.add`, :meth:`.remove`, :meth:`.update`,
    and :meth:`.clear`.

    This class is used internally for building column collections during
    construction of SQL constructs. For schema-level objects that require
    deduplication behavior, use :class:`.DedupeColumnCollection`.

    .. versionadded:: 2.1

    """

    __slots__ = ()

    def __init__(
        self, columns: Optional[Iterable[Tuple[_COLKEY, _COL_co]]] = None
    ):
        object.__setattr__(self, "_colset", set())
        object.__setattr__(self, "_index", {})
        object.__setattr__(
            self, "_proxy_index", collections.defaultdict(util.OrderedSet)
        )
        object.__setattr__(self, "_collection", [])
        if columns:
            self._initial_populate(columns)

    def _initial_populate(
        self, iter_: Iterable[Tuple[_COLKEY, _COL_co]]
    ) -> None:
        self._populate_separate_keys(iter_)

    def _populate_separate_keys(
        self, iter_: Iterable[Tuple[_COLKEY, _COL_co]]
    ) -> None:
        """populate from an iterator of (key, column)"""

        self._collection[:] = collection = [
            (k, c, _ColumnMetrics(self, c)) for k, c in iter_
        ]
        self._colset.update(c._deannotate() for _, c, _ in collection)
        self._index.update(
            {idx: (k, c) for idx, (k, c, _) in enumerate(collection)}
        )
        self._index.update({k: (k, col) for k, col, _ in reversed(collection)})

    def __getstate__(self) -> Dict[str, Any]:
        return {
            "_collection": [(k, c) for k, c, _ in self._collection],
            "_index": self._index,
        }

    def __setstate__(self, state: Dict[str, Any]) -> None:
        object.__setattr__(self, "_index", state["_index"])
        object.__setattr__(
            self, "_proxy_index", collections.defaultdict(util.OrderedSet)