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Fixed #31455 -- Added support for deferrable exclusion constraints on PostgreSQL.

This commit is contained in:
Ian Foote 2020-04-12 11:43:16 +01:00 committed by Mariusz Felisiak
parent 5d2f5dd4cc
commit b4068bc656
4 changed files with 145 additions and 7 deletions
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27
django/contrib/postgres/constraints.py
View File

@ -1,5 +1,5 @@
from django.db.backends.ddl_references import Statement, Table
from django.db.models import F, Q
from django.db.models import Deferrable, F, Q
from django.db.models.constraints import BaseConstraint
from django.db.models.sql import Query
@ -7,9 +7,12 @@ __all__ = ['ExclusionConstraint']
class ExclusionConstraint(BaseConstraint):
template = 'CONSTRAINT %(name)s EXCLUDE USING %(index_type)s (%(expressions)s)%(where)s'
template = 'CONSTRAINT %(name)s EXCLUDE USING %(index_type)s (%(expressions)s)%(where)s%(deferrable)s'
def __init__(self, *, name, expressions, index_type=None, condition=None):
def __init__(
self, *, name, expressions, index_type=None, condition=None,
deferrable=None,
):
if index_type and index_type.lower() not in {'gist', 'spgist'}:
raise ValueError(
'Exclusion constraints only support GiST or SP-GiST indexes.'
@ -28,9 +31,18 @@ class ExclusionConstraint(BaseConstraint):
raise ValueError(
'ExclusionConstraint.condition must be a Q instance.'
)
if condition and deferrable:
raise ValueError(
'ExclusionConstraint with conditions cannot be deferred.'
)
if not isinstance(deferrable, (type(None), Deferrable)):
raise ValueError(
'ExclusionConstraint.deferrable must be a Deferrable instance.'
)
self.expressions = expressions
self.index_type = index_type or 'GIST'
self.condition = condition
self.deferrable = deferrable
super().__init__(name=name)
def _get_expression_sql(self, compiler, connection, query):
@ -60,6 +72,7 @@ class ExclusionConstraint(BaseConstraint):
'index_type': self.index_type,
'expressions': ', '.join(expressions),
'where': ' WHERE (%s)' % condition if condition else '',
'deferrable': schema_editor._deferrable_constraint_sql(self.deferrable),
}
def create_sql(self, model, schema_editor):
@ -83,6 +96,8 @@ class ExclusionConstraint(BaseConstraint):
kwargs['condition'] = self.condition
if self.index_type.lower() != 'gist':
kwargs['index_type'] = self.index_type
if self.deferrable:
kwargs['deferrable'] = self.deferrable
return path, args, kwargs
def __eq__(self, other):
@ -91,14 +106,16 @@ class ExclusionConstraint(BaseConstraint):
self.name == other.name and
self.index_type == other.index_type and
self.expressions == other.expressions and
self.condition == other.condition
self.condition == other.condition and
self.deferrable == other.deferrable
)
return super().__eq__(other)
def __repr__(self):
return '<%s: index_type=%s, expressions=%s%s>' % (
return '<%s: index_type=%s, expressions=%s%s%s>' % (
self.__class__.__qualname__,
self.index_type,
self.expressions,
'' if self.condition is None else ', condition=%s' % self.condition,
'' if self.deferrable is None else ', deferrable=%s' % self.deferrable,
)

34
docs/ref/contrib/postgres/constraints.txt
View File

@ -14,7 +14,7 @@ PostgreSQL supports additional data integrity constraints available from the
.. versionadded:: 3.0
.. class:: ExclusionConstraint(*, name, expressions, index_type=None, condition=None)
.. class:: ExclusionConstraint(*, name, expressions, index_type=None, condition=None, deferrable=None)
Creates an exclusion constraint in the database. Internally, PostgreSQL
implements exclusion constraints using indexes. The default index type is
@ -76,6 +76,38 @@ a constraint to a subset of rows. For example,
These conditions have the same database restrictions as
:attr:`django.db.models.Index.condition`.
``deferrable``
--------------
.. attribute:: ExclusionConstraint.deferrable
.. versionadded:: 3.1
Set this parameter to create a deferrable exclusion constraint. Accepted values
are ``Deferrable.DEFERRED`` or ``Deferrable.IMMEDIATE``. For example::
from django.contrib.postgres.constraints import ExclusionConstraint
from django.contrib.postgres.fields import RangeOperators
from django.db.models import Deferrable
ExclusionConstraint(
name='exclude_overlapping_deferred',
expressions=[
('timespan', RangeOperators.OVERLAPS),
],
deferrable=Deferrable.DEFERRED,
)
By default constraints are not deferred. A deferred constraint will not be
enforced until the end of the transaction. An immediate constraint will be
enforced immediately after every command.
.. warning::
Deferred exclusion constraints may lead to a `performance penalty
<https://www.postgresql.org/docs/current/sql-createtable.html#id-1.9.3.85.9.4>`_.
Examples
--------

3
docs/releases/3.1.txt
View File

@ -176,6 +176,9 @@ Minor features
:class:`~django.contrib.postgres.search.SearchRank` allows rank
normalization.
* The new :attr:`.ExclusionConstraint.deferrable` attribute allows creating
deferrable exclusion constraints.
:mod:`django.contrib.redirects`
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

88
tests/postgres_tests/test_constraints.py
View File

@ -2,7 +2,7 @@ import datetime
from unittest import mock
from django.db import IntegrityError, connection, transaction
from django.db.models import CheckConstraint, F, Func, Q
from django.db.models import CheckConstraint, Deferrable, F, Func, Q
from django.utils import timezone
from . import PostgreSQLTestCase
@ -127,6 +127,25 @@ class ExclusionConstraintTests(PostgreSQLTestCase):
expressions=empty_expressions,
)
def test_invalid_deferrable(self):
msg = 'ExclusionConstraint.deferrable must be a Deferrable instance.'
with self.assertRaisesMessage(ValueError, msg):
ExclusionConstraint(
name='exclude_invalid_deferrable',
expressions=[(F('datespan'), RangeOperators.OVERLAPS)],
deferrable='invalid',
)
def test_deferrable_with_condition(self):
msg = 'ExclusionConstraint with conditions cannot be deferred.'
with self.assertRaisesMessage(ValueError, msg):
ExclusionConstraint(
name='exclude_invalid_condition',
expressions=[(F('datespan'), RangeOperators.OVERLAPS)],
condition=Q(cancelled=False),
deferrable=Deferrable.DEFERRED,
)
def test_repr(self):
constraint = ExclusionConstraint(
name='exclude_overlapping',
@ -151,6 +170,16 @@ class ExclusionConstraintTests(PostgreSQLTestCase):
"<ExclusionConstraint: index_type=SPGiST, expressions=["
"(F(datespan), '-|-')], condition=(AND: ('cancelled', False))>",
)
constraint = ExclusionConstraint(
name='exclude_overlapping',
expressions=[(F('datespan'), RangeOperators.ADJACENT_TO)],
deferrable=Deferrable.IMMEDIATE,
)
self.assertEqual(
repr(constraint),
"<ExclusionConstraint: index_type=GIST, expressions=["
"(F(datespan), '-|-')], deferrable=Deferrable.IMMEDIATE>",
)
def test_eq(self):
constraint_1 = ExclusionConstraint(
@ -173,11 +202,30 @@ class ExclusionConstraintTests(PostgreSQLTestCase):
expressions=[('datespan', RangeOperators.OVERLAPS)],
condition=Q(cancelled=False),
)
constraint_4 = ExclusionConstraint(
name='exclude_overlapping',
expressions=[
('datespan', RangeOperators.OVERLAPS),
('room', RangeOperators.EQUAL),
],
deferrable=Deferrable.DEFERRED,
)
constraint_5 = ExclusionConstraint(
name='exclude_overlapping',
expressions=[
('datespan', RangeOperators.OVERLAPS),
('room', RangeOperators.EQUAL),
],
deferrable=Deferrable.IMMEDIATE,
)
self.assertEqual(constraint_1, constraint_1)
self.assertEqual(constraint_1, mock.ANY)
self.assertNotEqual(constraint_1, constraint_2)
self.assertNotEqual(constraint_1, constraint_3)
self.assertNotEqual(constraint_1, constraint_4)
self.assertNotEqual(constraint_2, constraint_3)
self.assertNotEqual(constraint_2, constraint_4)
self.assertNotEqual(constraint_4, constraint_5)
self.assertNotEqual(constraint_1, object())
def test_deconstruct(self):
@ -223,6 +271,21 @@ class ExclusionConstraintTests(PostgreSQLTestCase):
'condition': Q(cancelled=False),
})
def test_deconstruct_deferrable(self):
constraint = ExclusionConstraint(
name='exclude_overlapping',
expressions=[('datespan', RangeOperators.OVERLAPS)],
deferrable=Deferrable.DEFERRED,
)
path, args, kwargs = constraint.deconstruct()
self.assertEqual(path, 'django.contrib.postgres.constraints.ExclusionConstraint')
self.assertEqual(args, ())
self.assertEqual(kwargs, {
'name': 'exclude_overlapping',
'expressions': [('datespan', RangeOperators.OVERLAPS)],
'deferrable': Deferrable.DEFERRED,
})
def _test_range_overlaps(self, constraint):
# Create exclusion constraint.
self.assertNotIn(constraint.name, self.get_constraints(HotelReservation._meta.db_table))
@ -327,3 +390,26 @@ class ExclusionConstraintTests(PostgreSQLTestCase):
RangesModel.objects.create(ints=(10, 20))
RangesModel.objects.create(ints=(10, 19))
RangesModel.objects.create(ints=(51, 60))
def test_range_adjacent_initially_deferred(self):
constraint_name = 'ints_adjacent_deferred'
self.assertNotIn(constraint_name, self.get_constraints(RangesModel._meta.db_table))
constraint = ExclusionConstraint(
name=constraint_name,
expressions=[('ints', RangeOperators.ADJACENT_TO)],
deferrable=Deferrable.DEFERRED,
)
with connection.schema_editor() as editor:
editor.add_constraint(RangesModel, constraint)
self.assertIn(constraint_name, self.get_constraints(RangesModel._meta.db_table))
RangesModel.objects.create(ints=(20, 50))
adjacent_range = RangesModel.objects.create(ints=(10, 20))
# Constraint behavior can be changed with SET CONSTRAINTS.
with self.assertRaises(IntegrityError):
with transaction.atomic(), connection.cursor() as cursor:
quoted_name = connection.ops.quote_name(constraint_name)
cursor.execute('SET CONSTRAINTS %s IMMEDIATE' % quoted_name)
# Remove adjacent range before the end of transaction.
adjacent_range.delete()
RangesModel.objects.create(ints=(10, 19))
RangesModel.objects.create(ints=(51, 60))