196 lines
8.0 KiB
Python
196 lines
8.0 KiB
Python
import warnings
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from django.contrib.postgres.indexes import OpClass
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from django.db import NotSupportedError
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from django.db.backends.ddl_references import Expressions, Statement, Table
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from django.db.models import Deferrable, F, Q
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from django.db.models.constraints import BaseConstraint
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from django.db.models.expressions import ExpressionList
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from django.db.models.indexes import IndexExpression
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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 = 'CONSTRAINT %(name)s EXCLUDE USING %(index_type)s (%(expressions)s)%(include)s%(where)s%(deferrable)s'
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def __init__(
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self, *, name, expressions, index_type=None, condition=None,
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deferrable=None, include=None, opclasses=(),
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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
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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(
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'ExclusionConstraint.condition must be a Q instance.'
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)
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if condition and deferrable:
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raise ValueError(
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'ExclusionConstraint with conditions cannot be deferred.'
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)
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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(
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'ExclusionConstraint.include must be a list or tuple.'
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)
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if not isinstance(opclasses, (list, tuple)):
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raise ValueError(
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'ExclusionConstraint.opclasses must be a list or tuple.'
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)
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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)
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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 = [model._meta.get_field(field_name).column for field_name in self.include]
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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(table, expressions, compiler, schema_editor.quote_value),
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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 and
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self.index_type.lower() == 'gist' and
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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 and
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self.index_type.lower() == 'spgist' and
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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 and
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self.index_type == other.index_type and
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self.expressions == other.expressions and
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self.condition == other.condition and
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self.deferrable == other.deferrable and
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self.include == other.include and
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self.opclasses == other.opclasses
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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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