from copy import copy
from typing import TYPE_CHECKING, List, Optional, Tuple
from pypika import Table
from pypika.terms import Criterion
from tortoise.exceptions import OperationalError
from tortoise.fields.relational import (
BackwardFKRelation,
ManyToManyFieldInstance,
RelationalField,
)
if TYPE_CHECKING: # pragma: nocoverage
from tortoise.queryset import QuerySet
def _get_joins_for_related_field(
table: Table, related_field: RelationalField, related_field_name: str
) -> List[Tuple[Table, Criterion]]:
required_joins = []
related_table: Table = related_field.related_model._meta.basetable
if isinstance(related_field, ManyToManyFieldInstance):
through_table = Table(related_field.through)
required_joins.append(
(
through_table,
table[related_field.model._meta.db_pk_column]
== through_table[related_field.backward_key],
)
)
required_joins.append(
(
related_table,
through_table[related_field.forward_key]
== related_table[related_field.related_model._meta.db_pk_column],
)
)
elif isinstance(related_field, BackwardFKRelation):
to_field_source_field = (
related_field.to_field_instance.source_field
or related_field.to_field_instance.model_field_name
)
if table == related_table:
related_table = related_table.as_(f"{table.get_table_name()}__{related_field_name}")
required_joins.append(
(
related_table,
table[to_field_source_field] == related_table[related_field.relation_source_field],
)
)
else:
to_field_source_field = (
related_field.to_field_instance.source_field
or related_field.to_field_instance.model_field_name
)
from_field = related_field.model._meta.fields_map[related_field.source_field] # type: ignore
from_field_source_field = from_field.source_field or from_field.model_field_name
related_table = related_table.as_(f"{table.get_table_name()}__{related_field_name}")
required_joins.append(
(
related_table,
related_table[to_field_source_field] == table[from_field_source_field],
)
)
return required_joins
class EmptyCriterion(Criterion): # type: ignore
def __or__(self, other: Criterion) -> Criterion:
return other
def __and__(self, other: Criterion) -> Criterion:
return other
def __bool__(self) -> bool:
return False
def _and(left: Criterion, right: Criterion) -> Criterion:
if left and not right:
return left
return left & right
def _or(left: Criterion, right: Criterion) -> Criterion:
if left and not right:
return left
return left | right
class QueryModifier:
"""
Internal structure used to generate SQL Queries.
"""
def __init__(
self,
where_criterion: Optional[Criterion] = None,
joins: Optional[List[Tuple[Table, Criterion]]] = None,
having_criterion: Optional[Criterion] = None,
) -> None:
self.where_criterion: Criterion = where_criterion or EmptyCriterion()
self.joins = joins if joins else []
self.having_criterion: Criterion = having_criterion or EmptyCriterion()
def __and__(self, other: "QueryModifier") -> "QueryModifier":
return QueryModifier(
where_criterion=_and(self.where_criterion, other.where_criterion),
joins=self.joins + other.joins,
having_criterion=_and(self.having_criterion, other.having_criterion),
)
def __or__(self, other: "QueryModifier") -> "QueryModifier":
if self.having_criterion or other.having_criterion:
# TODO: This could be optimized?
result_having_criterion = _or(
_and(self.where_criterion, self.having_criterion),
_and(other.where_criterion, other.having_criterion),
)
return QueryModifier(
joins=self.joins + other.joins, having_criterion=result_having_criterion
)
if self.where_criterion and other.where_criterion:
return QueryModifier(
where_criterion=self.where_criterion | other.where_criterion,
joins=self.joins + other.joins,
)
return QueryModifier(
where_criterion=self.where_criterion or other.where_criterion,
joins=self.joins + other.joins,
)
def __invert__(self) -> "QueryModifier":
if not self.where_criterion and not self.having_criterion:
return QueryModifier(joins=self.joins)
if self.having_criterion:
# TODO: This could be optimized?
return QueryModifier(
joins=self.joins,
having_criterion=_and(self.where_criterion, self.having_criterion).negate(),
)
return QueryModifier(where_criterion=self.where_criterion.negate(), joins=self.joins)
def get_query_modifiers(self) -> Tuple[Criterion, List[Tuple[Table, Criterion]], Criterion]:
"""
Returns a tuple of the query criterion.
"""
return self.where_criterion, self.joins, self.having_criterion
[docs]class Prefetch:
"""
Prefetcher container. One would directly use this when wanting to attach a custom QuerySet
for specialised prefetching.
:param relation: Related field name.
:param queryset: Custom QuerySet to use for prefetching.
:param to_attr: Sets the result of the prefetch operation to a custom attribute.
"""
__slots__ = ("relation", "queryset", "to_attr")
def __init__(self, relation: str, queryset: "QuerySet", to_attr: Optional[str] = None) -> None:
self.to_attr = to_attr
self.relation = relation
self.queryset = queryset
self.queryset.query = copy(self.queryset.model._meta.basequery)
[docs] def resolve_for_queryset(self, queryset: "QuerySet") -> None:
"""
Called internally to generate prefetching query.
:param queryset: Custom QuerySet to use for prefetching.
:raises OperationalError: If field does not exist in model.
"""
first_level_field, __, forwarded_prefetch = self.relation.partition("__")
if first_level_field not in queryset.model._meta.fetch_fields:
raise OperationalError(
f"relation {first_level_field} for {queryset.model._meta.db_table} not found"
)
if forwarded_prefetch:
if first_level_field not in queryset._prefetch_map.keys():
queryset._prefetch_map[first_level_field] = set()
queryset._prefetch_map[first_level_field].add(
Prefetch(forwarded_prefetch, self.queryset, to_attr=self.to_attr)
)
else:
queryset._prefetch_queries.setdefault(first_level_field, []).append(
(self.to_attr, self.queryset)
)