ormar/docs/api/models/mixins/prefetch-query-mixin.md

models.mixins.prefetch_mixin

PrefetchQueryMixin Objects

class PrefetchQueryMixin(RelationMixin)

Used in PrefetchQuery to extract ids and names of models to prefetch.

get_clause_target_and_filter_column_name

 | @staticmethod
 | get_clause_target_and_filter_column_name(parent_model: Type["Model"], target_model: Type["Model"], reverse: bool, related: str) -> Tuple[Type["Model"], str]

Returns Model on which query clause should be performed and name of the column.

Arguments:

• parent_model (Type[Model]): related model that the relation lead to
• target_model (Type[Model]): model on which query should be perfomed
• reverse (bool): flag if the relation is reverse
• related (str): name of the relation field

Returns:

(Tuple[Type[Model], str]): Model on which query clause should be performed and name of the column

get_column_name_for_id_extraction

 | @staticmethod
 | get_column_name_for_id_extraction(parent_model: Type["Model"], reverse: bool, related: str, use_raw: bool) -> str

Returns name of the column that should be used to extract ids from model. Depending on the relation side it's either primary key column of parent model or field name specified by related parameter.

Arguments:

• parent_model (Type[Model]): model from which id column should be extracted
• reverse (bool): flag if the relation is reverse
• related (str): name of the relation field
• use_raw (bool): flag if aliases or field names should be used

Returns:

():

get_related_field_name

 | @classmethod
 | get_related_field_name(cls, target_field: Type["ForeignKeyField"]) -> str

Returns name of the relation field that should be used in prefetch query. This field is later used to register relation in prefetch query, populate relations dict, and populate nested model in prefetch query.

Arguments:

• target_field (Type[BaseField]): relation field that should be used in prefetch

Returns:

(str): name of the field

get_filtered_names_to_extract

 | @classmethod
 | get_filtered_names_to_extract(cls, prefetch_dict: Dict) -> List

Returns list of related fields names that should be followed to prefetch related models from.

List of models is translated into dict to assure each model is extracted only once in one query, that's why this function accepts prefetch_dict not list.

Only relations from current model are returned.

Arguments:

• prefetch_dict (Dict): dictionary of fields to extract

Returns:

(List): list of fields names to extract