101 lines
3.0 KiB
Markdown
101 lines
3.0 KiB
Markdown
<a name="models.mixins.prefetch_mixin"></a>
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# models.mixins.prefetch\_mixin
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<a name="models.mixins.prefetch_mixin.PrefetchQueryMixin"></a>
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## PrefetchQueryMixin Objects
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```python
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class PrefetchQueryMixin(RelationMixin)
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```
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Used in PrefetchQuery to extract ids and names of models to prefetch.
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<a name="models.mixins.prefetch_mixin.PrefetchQueryMixin.get_clause_target_and_filter_column_name"></a>
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#### get\_clause\_target\_and\_filter\_column\_name
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```python
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| @staticmethod
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| get_clause_target_and_filter_column_name(parent_model: Type["Model"], target_model: Type["Model"], reverse: bool, related: str) -> Tuple[Type["Model"], str]
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```
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Returns Model on which query clause should be performed and name of the column.
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**Arguments**:
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- `parent_model` (`Type[Model]`): related model that the relation lead to
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- `target_model` (`Type[Model]`): model on which query should be perfomed
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- `reverse` (`bool`): flag if the relation is reverse
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- `related` (`str`): name of the relation field
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**Returns**:
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`Tuple[Type[Model], str]`: Model on which query clause should be performed and name of the column
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<a name="models.mixins.prefetch_mixin.PrefetchQueryMixin.get_column_name_for_id_extraction"></a>
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#### get\_column\_name\_for\_id\_extraction
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```python
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| @staticmethod
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| get_column_name_for_id_extraction(parent_model: Type["Model"], reverse: bool, related: str, use_raw: bool) -> str
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```
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Returns name of the column that should be used to extract ids from model.
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Depending on the relation side it's either primary key column of parent model
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or field name specified by related parameter.
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**Arguments**:
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- `parent_model` (`Type[Model]`): model from which id column should be extracted
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- `reverse` (`bool`): flag if the relation is reverse
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- `related` (`str`): name of the relation field
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- `use_raw` (`bool`): flag if aliases or field names should be used
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**Returns**:
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<a name="models.mixins.prefetch_mixin.PrefetchQueryMixin.get_related_field_name"></a>
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#### get\_related\_field\_name
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```python
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| @classmethod
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| get_related_field_name(cls, target_field: "ForeignKeyField") -> str
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```
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Returns name of the relation field that should be used in prefetch query.
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This field is later used to register relation in prefetch query,
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populate relations dict, and populate nested model in prefetch query.
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**Arguments**:
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- `target_field` (`Type[BaseField]`): relation field that should be used in prefetch
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**Returns**:
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`str`: name of the field
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<a name="models.mixins.prefetch_mixin.PrefetchQueryMixin.get_filtered_names_to_extract"></a>
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#### get\_filtered\_names\_to\_extract
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```python
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| @classmethod
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| get_filtered_names_to_extract(cls, prefetch_dict: Dict) -> List
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```
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Returns list of related fields names that should be followed to prefetch related
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models from.
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List of models is translated into dict to assure each model is extracted only
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once in one query, that's why this function accepts prefetch_dict not list.
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Only relations from current model are returned.
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**Arguments**:
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- `prefetch_dict` (`Dict`): dictionary of fields to extract
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**Returns**:
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`List`: list of fields names to extract
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