Source code for django.contrib.postgres.constraints

import warnings

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
from django.utils.deprecation import RemovedInDjango50Warning

__all__ = ["ExclusionConstraint"]

class ExclusionConstraintExpression(IndexExpression):
    template = "%(expressions)s WITH %(operator)s"

[docs]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, opclasses=(), 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, (type(None), Q)): raise ValueError("ExclusionConstraint.condition must be a Q instance.") if not isinstance(deferrable, (type(None), Deferrable)): raise ValueError( "ExclusionConstraint.deferrable must be a Deferrable instance." ) if not isinstance(include, (type(None), list, tuple)): raise ValueError("ExclusionConstraint.include must be a list or tuple.") if not isinstance(opclasses, (list, tuple)): raise ValueError("ExclusionConstraint.opclasses must be a list or tuple.") if opclasses and len(expressions) != len(opclasses): raise ValueError( "ExclusionConstraint.expressions and " "ExclusionConstraint.opclasses must have the same number of " "elements." ) self.expressions = expressions self.index_type = index_type or "GIST" self.condition = condition self.deferrable = deferrable self.include = tuple(include) if include else () self.opclasses = opclasses if self.opclasses: warnings.warn( "The opclasses argument is deprecated in favor of using " "django.contrib.postgres.indexes.OpClass in " "ExclusionConstraint.expressions.", category=RemovedInDjango50Warning, stacklevel=2, ) super().__init__(name=name, 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) try: expression = OpClass(expression, self.opclasses[idx]) except IndexError: pass 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(, 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(, ) 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 if self.opclasses: kwargs["opclasses"] = self.opclasses return path, args, kwargs def __eq__(self, other): if isinstance(other, self.__class__): return ( == 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.opclasses == other.opclasses 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>" % ( self.__class__.__qualname__, repr(self.index_type), repr(self.expressions), repr(, "" 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 not self.opclasses else " opclasses=%s" % repr(self.opclasses), ) 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 in exclude: return else: for expr in expression.flatten(): if isinstance(expr, F) and 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()) else: if (self.condition & Exists(queryset.filter(self.condition))).check( replacement_map, using=using ): raise ValidationError(self.get_violation_error_message())
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