# models.mixins.relation\_mixin ## RelationMixin Objects ```python class RelationMixin() ``` Used to return relation fields/names etc. from given model #### extract\_db\_own\_fields ```python | @classmethod | extract_db_own_fields(cls) -> Set ``` Returns only fields that are stored in the own database table, exclude all related fields. **Returns**: `(Set)`: set of model fields with relation fields excluded #### extract\_related\_fields ```python | @classmethod | extract_related_fields(cls) -> List ``` Returns List of ormar Fields for all relations declared on a model. List is cached in cls._related_fields for quicker access. **Returns**: `(List)`: list of related fields #### extract\_through\_names ```python | @classmethod | extract_through_names(cls) -> Set ``` Extracts related fields through names which are shortcuts to through models. **Returns**: `(Set)`: set of related through fields names #### extract\_related\_names ```python | @classmethod | extract_related_names(cls) -> Set[str] ``` Returns List of fields names for all relations declared on a model. List is cached in cls._related_names for quicker access. **Returns**: `(Set)`: set of related fields names #### \_extract\_db\_related\_names ```python | @classmethod | _extract_db_related_names(cls) -> Set ``` Returns only fields that are stored in the own database table, exclude related fields that are not stored as foreign keys on given model. **Returns**: `(Set)`: set of model fields with non fk relation fields excluded #### \_exclude\_related\_names\_not\_required ```python | @classmethod | _exclude_related_names_not_required(cls, nested: bool = False) -> Set ``` Returns a set of non mandatory related models field names. For a main model (not nested) only nullable related field names are returned, for nested models all related models are returned. **Arguments**: - `nested (bool)`: flag setting nested models (child of previous one, not main one) **Returns**: `(Set)`: set of non mandatory related fields #### \_iterate\_related\_models ```python | @classmethod | _iterate_related_models(cls, visited: Set[Union[Type["Model"], Type["RelationMixin"]]] = None, source_relation: str = None, source_model: Union[Type["Model"], Type["RelationMixin"]] = None) -> List[str] ``` Iterates related models recursively to extract relation strings of nested not visited models. **Arguments**: - `visited (Set[str])`: set of already visited models - `source_relation (str)`: name of the current relation - `source_model (Type["Model"])`: model from which relation comes in nested relations **Returns**: `(List[str])`: list of relation strings to be passed to select_related