Function _apply_indexes_fast

xarray/core/indexes.py:2150–2180

(indexes: Indexes[Index], args: Mapping[Any, Any], func: str)

def _apply_indexes_fast(indexes: Indexes[Index], args: Mapping[Any, Any], func: str):
    # This function avoids the call to indexes.group_by_index
    # which is really slow when repeatedly iterating through
    # an array. However, it fails to return the correct ID for
    # multi-index arrays
    indexes_fast, coords = indexes._indexes, indexes._variables

    new_indexes: dict[Hashable, Index] = dict(indexes_fast.items())
    new_index_variables: dict[Hashable, Variable] = {}
    for name, index in indexes_fast.items():
        coord = coords[name]
        if hasattr(coord, "_indexes"):
            index_vars = {n: coords[n] for n in coord._indexes}
        else:
            index_vars = {name: coord}
        index_dims = {d for var in index_vars.values() for d in var.dims}
        index_args = {k: v for k, v in args.items() if k in index_dims}

        if index_args:
            new_index = getattr(index, func)(index_args)
            if new_index is not None:
                new_indexes.update(dict.fromkeys(index_vars, new_index))
                if new_index is index:
                    new_index_vars = index_vars
                else:
                    new_index_vars = new_index.create_variables(index_vars)
                new_index_variables.update(new_index_vars)
            else:
                for k in index_vars:
                    new_indexes.pop(k, None)
    return new_indexes, new_index_variables


def _apply_indexes(