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