245 lines
10 KiB
Python
245 lines
10 KiB
Python
import warnings
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from django.contrib.postgres.indexes import OpClass
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from django.core.exceptions import ValidationError
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from django.db import DEFAULT_DB_ALIAS, NotSupportedError
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from django.db.backends.ddl_references import Expressions, Statement, Table
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from django.db.models import BaseConstraint, Deferrable, F, Q
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from django.db.models.expressions import Exists, ExpressionList
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from django.db.models.indexes import IndexExpression
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from django.db.models.lookups import PostgresOperatorLookup
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from django.db.models.sql import Query
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from django.utils.deprecation import RemovedInDjango50Warning
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__all__ = ["ExclusionConstraint"]
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class ExclusionConstraintExpression(IndexExpression):
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template = "%(expressions)s WITH %(operator)s"
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class ExclusionConstraint(BaseConstraint):
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template = (
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"CONSTRAINT %(name)s EXCLUDE USING %(index_type)s "
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"(%(expressions)s)%(include)s%(where)s%(deferrable)s"
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)
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def __init__(
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self,
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*,
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name,
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expressions,
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index_type=None,
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condition=None,
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deferrable=None,
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include=None,
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opclasses=(),
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violation_error_message=None,
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):
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if index_type and index_type.lower() not in {"gist", "spgist"}:
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raise ValueError(
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"Exclusion constraints only support GiST or SP-GiST indexes."
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)
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if not expressions:
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raise ValueError(
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"At least one expression is required to define an exclusion "
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"constraint."
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)
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if not all(
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isinstance(expr, (list, tuple)) and len(expr) == 2 for expr in expressions
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):
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raise ValueError("The expressions must be a list of 2-tuples.")
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if not isinstance(condition, (type(None), Q)):
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raise ValueError("ExclusionConstraint.condition must be a Q instance.")
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if condition and deferrable:
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raise ValueError("ExclusionConstraint with conditions cannot be deferred.")
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if not isinstance(deferrable, (type(None), Deferrable)):
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raise ValueError(
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"ExclusionConstraint.deferrable must be a Deferrable instance."
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)
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if not isinstance(include, (type(None), list, tuple)):
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raise ValueError("ExclusionConstraint.include must be a list or tuple.")
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if not isinstance(opclasses, (list, tuple)):
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raise ValueError("ExclusionConstraint.opclasses must be a list or tuple.")
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if opclasses and len(expressions) != len(opclasses):
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raise ValueError(
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"ExclusionConstraint.expressions and "
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"ExclusionConstraint.opclasses must have the same number of "
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"elements."
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)
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self.expressions = expressions
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self.index_type = index_type or "GIST"
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self.condition = condition
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self.deferrable = deferrable
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self.include = tuple(include) if include else ()
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self.opclasses = opclasses
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if self.opclasses:
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warnings.warn(
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"The opclasses argument is deprecated in favor of using "
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"django.contrib.postgres.indexes.OpClass in "
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"ExclusionConstraint.expressions.",
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category=RemovedInDjango50Warning,
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stacklevel=2,
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)
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super().__init__(name=name, violation_error_message=violation_error_message)
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def _get_expressions(self, schema_editor, query):
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expressions = []
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for idx, (expression, operator) in enumerate(self.expressions):
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if isinstance(expression, str):
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expression = F(expression)
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try:
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expression = OpClass(expression, self.opclasses[idx])
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except IndexError:
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pass
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expression = ExclusionConstraintExpression(expression, operator=operator)
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expression.set_wrapper_classes(schema_editor.connection)
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expressions.append(expression)
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return ExpressionList(*expressions).resolve_expression(query)
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def _get_condition_sql(self, compiler, schema_editor, query):
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if self.condition is None:
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return None
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where = query.build_where(self.condition)
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sql, params = where.as_sql(compiler, schema_editor.connection)
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return sql % tuple(schema_editor.quote_value(p) for p in params)
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def constraint_sql(self, model, schema_editor):
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query = Query(model, alias_cols=False)
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compiler = query.get_compiler(connection=schema_editor.connection)
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expressions = self._get_expressions(schema_editor, query)
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table = model._meta.db_table
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condition = self._get_condition_sql(compiler, schema_editor, query)
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include = [
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model._meta.get_field(field_name).column for field_name in self.include
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]
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return Statement(
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self.template,
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table=Table(table, schema_editor.quote_name),
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name=schema_editor.quote_name(self.name),
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index_type=self.index_type,
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expressions=Expressions(
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table, expressions, compiler, schema_editor.quote_value
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),
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where=" WHERE (%s)" % condition if condition else "",
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include=schema_editor._index_include_sql(model, include),
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deferrable=schema_editor._deferrable_constraint_sql(self.deferrable),
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)
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def create_sql(self, model, schema_editor):
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self.check_supported(schema_editor)
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return Statement(
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"ALTER TABLE %(table)s ADD %(constraint)s",
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table=Table(model._meta.db_table, schema_editor.quote_name),
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constraint=self.constraint_sql(model, schema_editor),
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)
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def remove_sql(self, model, schema_editor):
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return schema_editor._delete_constraint_sql(
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schema_editor.sql_delete_check,
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model,
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schema_editor.quote_name(self.name),
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)
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def check_supported(self, schema_editor):
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if (
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self.include
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and self.index_type.lower() == "gist"
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and not schema_editor.connection.features.supports_covering_gist_indexes
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):
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raise NotSupportedError(
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"Covering exclusion constraints using a GiST index require "
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"PostgreSQL 12+."
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)
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if (
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self.include
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and self.index_type.lower() == "spgist"
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and not schema_editor.connection.features.supports_covering_spgist_indexes
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):
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raise NotSupportedError(
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"Covering exclusion constraints using an SP-GiST index "
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"require PostgreSQL 14+."
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)
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def deconstruct(self):
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path, args, kwargs = super().deconstruct()
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kwargs["expressions"] = self.expressions
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if self.condition is not None:
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kwargs["condition"] = self.condition
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if self.index_type.lower() != "gist":
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kwargs["index_type"] = self.index_type
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if self.deferrable:
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kwargs["deferrable"] = self.deferrable
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if self.include:
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kwargs["include"] = self.include
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if self.opclasses:
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kwargs["opclasses"] = self.opclasses
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return path, args, kwargs
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def __eq__(self, other):
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if isinstance(other, self.__class__):
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return (
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self.name == other.name
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and self.index_type == other.index_type
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and self.expressions == other.expressions
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and self.condition == other.condition
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and self.deferrable == other.deferrable
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and self.include == other.include
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and self.opclasses == other.opclasses
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and self.violation_error_message == other.violation_error_message
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)
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return super().__eq__(other)
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def __repr__(self):
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return "<%s: index_type=%s expressions=%s name=%s%s%s%s%s>" % (
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self.__class__.__qualname__,
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repr(self.index_type),
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repr(self.expressions),
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repr(self.name),
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"" if self.condition is None else " condition=%s" % self.condition,
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"" if self.deferrable is None else " deferrable=%r" % self.deferrable,
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"" if not self.include else " include=%s" % repr(self.include),
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"" if not self.opclasses else " opclasses=%s" % repr(self.opclasses),
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)
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def validate(self, model, instance, exclude=None, using=DEFAULT_DB_ALIAS):
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queryset = model._default_manager.using(using)
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replacement_map = instance._get_field_value_map(
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meta=model._meta, exclude=exclude
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)
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lookups = []
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for idx, (expression, operator) in enumerate(self.expressions):
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if isinstance(expression, str):
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expression = F(expression)
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if isinstance(expression, F):
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if exclude and expression.name in exclude:
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return
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rhs_expression = replacement_map.get(expression.name, expression)
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else:
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rhs_expression = expression.replace_references(replacement_map)
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if exclude:
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for expr in rhs_expression.flatten():
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if isinstance(expr, F) and expr.name in exclude:
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return
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# Remove OpClass because it only has sense during the constraint
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# creation.
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if isinstance(expression, OpClass):
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expression = expression.get_source_expressions()[0]
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if isinstance(rhs_expression, OpClass):
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rhs_expression = rhs_expression.get_source_expressions()[0]
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lookup = PostgresOperatorLookup(lhs=expression, rhs=rhs_expression)
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lookup.postgres_operator = operator
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lookups.append(lookup)
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queryset = queryset.filter(*lookups)
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model_class_pk = instance._get_pk_val(model._meta)
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if not instance._state.adding and model_class_pk is not None:
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queryset = queryset.exclude(pk=model_class_pk)
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if not self.condition:
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if queryset.exists():
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raise ValidationError(self.get_violation_error_message())
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else:
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if (self.condition & Exists(queryset.filter(self.condition))).check(
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replacement_map, using=using
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):
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raise ValidationError(self.get_violation_error_message())
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