230 lines
5.2 KiB
Markdown
230 lines
5.2 KiB
Markdown
<a name="queryset.join"></a>
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# queryset.join
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<a name="queryset.join.SqlJoin"></a>
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## SqlJoin Objects
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```python
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class SqlJoin()
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```
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<a name="queryset.join.SqlJoin.alias_manager"></a>
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#### alias\_manager
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```python
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| @property
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| alias_manager() -> AliasManager
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```
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Shortcut for ormar's model AliasManager stored on Meta.
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**Returns**:
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`(AliasManager)`: alias manager from model's Meta
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<a name="queryset.join.SqlJoin.to_table"></a>
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#### to\_table
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```python
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| @property
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| to_table() -> sqlalchemy.Table
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```
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Shortcut to table name of the next model
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**Returns**:
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`(str)`: name of the target table
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<a name="queryset.join.SqlJoin._on_clause"></a>
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#### \_on\_clause
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```python
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| _on_clause(previous_alias: str, from_clause: str, to_clause: str) -> text
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```
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Receives aliases and names of both ends of the join and combines them
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into one text clause used in joins.
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**Arguments**:
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- `previous_alias (str)`: alias of previous table
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- `from_clause (str)`: from table name
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- `to_clause (str)`: to table name
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**Returns**:
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`(sqlalchemy.text)`: clause combining all strings
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<a name="queryset.join.SqlJoin.build_join"></a>
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#### build\_join
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```python
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| build_join() -> Tuple[List, sqlalchemy.sql.select, List, OrderedDict]
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```
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Main external access point for building a join.
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Splits the join definition, updates fields and exclude_fields if needed,
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handles switching to through models for m2m relations, returns updated lists of
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used_aliases and sort_orders.
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**Returns**:
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`(Tuple[List[str], Join, List[TextClause], collections.OrderedDict])`: list of used aliases, select from, list of aliased columns, sort orders
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<a name="queryset.join.SqlJoin._forward_join"></a>
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#### \_forward\_join
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```python
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| _forward_join() -> None
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```
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Process actual join.
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Registers complex relation join on encountering of the duplicated alias.
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<a name="queryset.join.SqlJoin._process_following_joins"></a>
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#### \_process\_following\_joins
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```python
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| _process_following_joins() -> None
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```
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Iterates through nested models to create subsequent joins.
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<a name="queryset.join.SqlJoin._process_deeper_join"></a>
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#### \_process\_deeper\_join
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```python
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| _process_deeper_join(related_name: str, remainder: Any) -> None
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```
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Creates nested recurrent instance of SqlJoin for each nested join table,
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updating needed return params here as a side effect.
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Updated are:
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* self.used_aliases,
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* self.select_from,
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* self.columns,
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* self.sorted_orders,
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**Arguments**:
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- `related_name (str)`: name of the relation to follow
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- `remainder (Any)`: deeper tables if there are more nested joins
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<a name="queryset.join.SqlJoin._process_m2m_through_table"></a>
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#### \_process\_m2m\_through\_table
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```python
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| _process_m2m_through_table() -> None
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```
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Process Through table of the ManyToMany relation so that source table is
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linked to the through table (one additional join)
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Replaces needed parameters like:
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* self.next_model,
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* self.next_alias,
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* self.relation_name,
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* self.own_alias,
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* self.target_field
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To point to through model
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<a name="queryset.join.SqlJoin._process_m2m_related_name_change"></a>
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#### \_process\_m2m\_related\_name\_change
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```python
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| _process_m2m_related_name_change(reverse: bool = False) -> str
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```
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Extracts relation name to link join through the Through model declared on
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relation field.
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Changes the same names in order_by queries if they are present.
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**Arguments**:
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- `reverse (bool)`: flag if it's on_clause lookup - use reverse fields
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**Returns**:
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`(str)`: new relation name switched to through model field
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<a name="queryset.join.SqlJoin._process_join"></a>
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#### \_process\_join
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```python
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| _process_join() -> None
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```
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Resolves to and from column names and table names.
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Produces on_clause.
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Performs actual join updating select_from parameter.
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Adds aliases of required column to list of columns to include in query.
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Updates the used aliases list directly.
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Process order_by causes for non m2m relations.
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<a name="queryset.join.SqlJoin._verify_allowed_order_field"></a>
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#### \_verify\_allowed\_order\_field
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```python
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| _verify_allowed_order_field(order_by: str) -> None
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```
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Verifies if proper field string is used.
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**Arguments**:
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- `order_by (str)`: string with order by definition
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<a name="queryset.join.SqlJoin._get_alias_and_model"></a>
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#### \_get\_alias\_and\_model
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```python
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| _get_alias_and_model(order_by: str) -> Tuple[str, Type["Model"]]
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```
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Returns proper model and alias to be applied in the clause.
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**Arguments**:
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- `order_by (str)`: string with order by definition
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**Returns**:
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`(Tuple[str, Type["Model"]])`: alias and model to be used in clause
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<a name="queryset.join.SqlJoin._get_order_bys"></a>
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#### \_get\_order\_bys
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```python
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| _get_order_bys() -> None
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```
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Triggers construction of order bys if they are given.
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Otherwise by default each table is sorted by a primary key column asc.
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<a name="queryset.join.SqlJoin._get_to_and_from_keys"></a>
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#### \_get\_to\_and\_from\_keys
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```python
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| _get_to_and_from_keys() -> Tuple[str, str]
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```
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Based on the relation type, name of the relation and previous models and parts
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stored in JoinParameters it resolves the current to and from keys, which are
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different for ManyToMany relation, ForeignKey and reverse related of relations.
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**Returns**:
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`(Tuple[str, str])`: to key and from key
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