240 lines
8.4 KiB
Python
240 lines
8.4 KiB
Python
from typing import List, NamedTuple, TYPE_CHECKING, Tuple, Type
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import sqlalchemy
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from sqlalchemy import text
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import ormar # noqa I100
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from ormar.fields import BaseField
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from ormar.fields.foreign_key import ForeignKeyField
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if TYPE_CHECKING: # pragma no cover
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from ormar import Model
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class JoinParameters(NamedTuple):
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prev_model: Type["Model"]
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previous_alias: str
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from_table: str
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model_cls: Type["Model"]
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class Query:
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def __init__(
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self,
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model_cls: Type["Model"],
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filter_clauses: List,
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select_related: List,
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limit_count: int,
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offset: int,
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) -> None:
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self.query_offset = offset
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self.limit_count = limit_count
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self._select_related = select_related
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self.filter_clauses = filter_clauses
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self.model_cls = model_cls
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self.table = self.model_cls.Meta.table
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self.auto_related = []
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self.used_aliases = []
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self.already_checked = []
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self.select_from = None
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self.columns = None
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self.order_bys = None
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def build_select_expression(self) -> Tuple[sqlalchemy.sql.select, List[str]]:
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self.columns = list(self.table.columns)
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self.order_bys = [text(f"{self.table.name}.{self.model_cls.Meta.pkname}")]
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self.select_from = self.table
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# for key in self.model_cls.Meta.model_fields:
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# if (
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# not self.model_cls.Meta.model_fields[key].nullable
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# and isinstance(
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# self.model_cls.Meta.model_fields[key], ForeignKeyField,
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# )
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# and key not in self._select_related
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# ):
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# self._select_related = [key] + self._select_related
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start_params = JoinParameters(
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self.model_cls, "", self.table.name, self.model_cls
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)
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self._extract_auto_required_relations(prev_model=start_params.prev_model)
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self._include_auto_related_models()
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self._select_related.sort(key=lambda item: (-len(item), item))
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for item in self._select_related:
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join_parameters = JoinParameters(
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self.model_cls, "", self.table.name, self.model_cls
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)
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for part in item.split("__"):
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join_parameters = self._build_join_parameters(part, join_parameters)
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expr = sqlalchemy.sql.select(self.columns)
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expr = expr.select_from(self.select_from)
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expr = self._apply_expression_modifiers(expr)
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# print(expr.compile(compile_kwargs={"literal_binds": True}))
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self._reset_query_parameters()
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return expr, self._select_related
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@staticmethod
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def prefixed_columns(alias: str, table: sqlalchemy.Table) -> List[text]:
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return [
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text(f"{alias}_{table.name}.{column.name} as {alias}_{column.name}")
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for column in table.columns
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]
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@staticmethod
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def prefixed_table_name(alias: str, name: str) -> text:
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return text(f"{name} {alias}_{name}")
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@staticmethod
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def _field_is_a_foreign_key_and_no_circular_reference(
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field: Type[BaseField], field_name: str, rel_part: str
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) -> bool:
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return issubclass(field, ForeignKeyField) and field_name not in rel_part
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def _field_qualifies_to_deeper_search(
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self, field: ForeignKeyField, parent_virtual: bool, nested: bool, rel_part: str
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) -> bool:
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prev_part_of_related = "__".join(rel_part.split("__")[:-1])
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partial_match = any(
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[x.startswith(prev_part_of_related) for x in self._select_related]
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)
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already_checked = any(
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[x.startswith(rel_part) for x in (self.auto_related + self.already_checked)]
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)
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return (
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(field.virtual and parent_virtual)
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or (partial_match and not already_checked)
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) or not nested
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def on_clause(
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self, previous_alias: str, alias: str, from_clause: str, to_clause: str,
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) -> text:
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left_part = f"{alias}_{to_clause}"
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right_part = f"{previous_alias + '_' if previous_alias else ''}{from_clause}"
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return text(f"{left_part}={right_part}")
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def _build_join_parameters(
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self, part: str, join_params: JoinParameters
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) -> JoinParameters:
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model_cls = join_params.model_cls.Meta.model_fields[part].to
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to_table = model_cls.Meta.table.name
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alias = model_cls.Meta._orm_relationship_manager.resolve_relation_join(
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join_params.from_table, to_table
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)
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if alias not in self.used_aliases:
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if join_params.prev_model.Meta.model_fields[part].virtual:
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to_key = next(
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(
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v
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for k, v in model_cls.Meta.model_fields.items()
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if issubclass(v, ForeignKeyField)
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and v.to == join_params.prev_model
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),
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None,
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).name
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from_key = model_cls.Meta.pkname
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else:
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to_key = model_cls.Meta.pkname
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from_key = part
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on_clause = self.on_clause(
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previous_alias=join_params.previous_alias,
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alias=alias,
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from_clause=f"{join_params.from_table}.{from_key}",
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to_clause=f"{to_table}.{to_key}",
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)
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target_table = self.prefixed_table_name(alias, to_table)
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self.select_from = sqlalchemy.sql.outerjoin(
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self.select_from, target_table, on_clause
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)
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self.order_bys.append(text(f"{alias}_{to_table}.{model_cls.Meta.pkname}"))
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self.columns.extend(self.prefixed_columns(alias, model_cls.Meta.table))
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self.used_aliases.append(alias)
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previous_alias = alias
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from_table = to_table
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prev_model = model_cls
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return JoinParameters(prev_model, previous_alias, from_table, model_cls)
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def _extract_auto_required_relations(
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self,
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prev_model: Type["Model"],
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rel_part: str = "",
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nested: bool = False,
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parent_virtual: bool = False,
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) -> None:
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for field_name, field in prev_model.Meta.model_fields.items():
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if self._field_is_a_foreign_key_and_no_circular_reference(
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field, field_name, rel_part
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):
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rel_part = field_name if not rel_part else rel_part + "__" + field_name
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if not field.nullable:
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if rel_part not in self._select_related:
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new_related = (
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"__".join(rel_part.split("__")[:-1])
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if len(rel_part.split("__")) > 1
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else rel_part
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)
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self.auto_related.append(new_related)
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rel_part = ""
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elif self._field_qualifies_to_deeper_search(
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field, parent_virtual, nested, rel_part
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):
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self._extract_auto_required_relations(
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prev_model=field.to,
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rel_part=rel_part,
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nested=True,
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parent_virtual=field.virtual,
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)
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else:
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self.already_checked.append(rel_part)
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rel_part = ""
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def _include_auto_related_models(self) -> None:
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if self.auto_related:
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new_joins = []
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for join in self._select_related:
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if not any([x.startswith(join) for x in self.auto_related]):
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new_joins.append(join)
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self._select_related = new_joins + self.auto_related
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def _apply_expression_modifiers(
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self, expr: sqlalchemy.sql.select
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) -> sqlalchemy.sql.select:
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if self.filter_clauses:
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if len(self.filter_clauses) == 1:
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clause = self.filter_clauses[0]
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else:
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clause = sqlalchemy.sql.and_(*self.filter_clauses)
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expr = expr.where(clause)
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if self.limit_count:
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expr = expr.limit(self.limit_count)
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if self.query_offset:
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expr = expr.offset(self.query_offset)
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for order in self.order_bys:
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expr = expr.order_by(order)
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return expr
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def _reset_query_parameters(self) -> None:
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self.select_from = None
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self.columns = None
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self.order_bys = None
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self.auto_related = []
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self.used_aliases = []
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self.already_checked = []
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