Improved Query join promotion logic (ecaba360) · Commits · Dom Sekotill / django

django/db/models/sql/query.py

+82 −34

Original line number	Diff line number	Diff line
		@@ -901,15 +901,15 @@ class Query(object):
		# Not all tables need to be joined to anything. No join type
		# means the later columns are ignored.
		join_type = None
		elif outer_if_first or self.alias_map[lhs].join_type == self.LOUTER:
		# We need to use LOUTER join if asked by outer_if_first or if the
		# LHS table is left-joined in the query.
		elif self.alias_map[lhs].join_type == self.LOUTER:
		join_type = self.LOUTER
		else:
		join_type = self.INNER
		join = JoinInfo(table, alias, join_type, lhs, join_cols or ((None, None),), nullable,
		join_field)
		self.alias_map[alias] = join
		if outer_if_first:
		self.promote_joins([alias])
		if connection in self.join_map:
		self.join_map[connection] += (alias,)
		else:
		@@ -1004,17 +1004,14 @@ class Query(object):
		# - this is an annotation over a model field
		# then we need to explore the joins that are required.

		# Join promotion note - we must not remove any rows here, so use
		# outer join if there isn't any existing join.
		field, sources, opts, join_list, path = self.setup_joins(
		field_list, opts, self.get_initial_alias())
		field_list, opts, self.get_initial_alias(), outer_if_first=True)

		# Process the join chain to see if it can be trimmed
		targets, _, join_list = self.trim_joins(sources, join_list, path)

		# If the aggregate references a model or field that requires a join,
		# those joins must be LEFT OUTER - empty join rows must be returned
		# in order for zeros to be returned for those aggregates.
		self.promote_joins(join_list)

		col = targets[0].column
		source = sources[0]
		col = (join_list[-1], col)
		@@ -1089,8 +1086,69 @@ class Query(object):
		break
		return lookup_type, lookup_parts

		def promote_filter_joins(self, join_list, can_reuse, lookup_type, value,
		current_negated, connector):
		# If the comparison is against NULL, we may need to use some left
		# outer joins when creating the join chain.
		#
		# The logic here is that every isnull lookup in non-negated case is
		# promoted when the connector is OR. In the AND case we do this only
		# for first creation of the join. Join demotion happens reverse to
		# this - demote always in AND case, first use only in OR case.
		#
		# In the OR case, a null row for the join can yield results for isnull
		# lookup. But in the AND case that can't happen (assuming the other
		# joins require non-null values) - if the join produces null row, then
		# the ANDed condition that requires non-null value will not match, and
		# hence the whole condition will not match.
		#
		# Consider case: (a__something & a__isnull=True)
		#
		# If a is null here, then a__something can't match anything (unless
		# it also requires outer join), and thus the join doesn't need to be
		# promoted by a__isnull.
		#
		# The connector isn't the only condition for removing join promotion.
		# The already created joins also play a role here. Above, in the
		# AND case, we don't want to promote the isnull lookup. But if we have
		# only (a__isnull), then we must promote it. To see if a join needs
		# to be promoted we use the seen joins inside this filter clause. That
		# is contained in can_reuse - those are actually joins that have been
		# built by this filter clause.
		#
		# Similar reasoning applies for join demotion, exception we demote
		# joins in the AND case always, and never demote them in the OR case.
		#
		# Some examples: (a__name__isnull=True \| a__type=1)
		# When a__name__isnull is seen it is promoted (it is first creation of
		# that join). a__type will not demote the join as it isn't first
		# "a" join in the filter condition, and this is ORed query.
		# (a__name__isnull=True & a__type=1)
		# Here again a__name__isnull will create an outer join, but now a__type
		# will demote the join back to inner join as the connector is AND.
		# (a__type=1 & a__name__isnull=True)
		# a__type will create inner join, a__name__isnull will not promote it
		# to outer join as this is AND case and this isn't first use of the
		# join. For completeness:
		# (a__type=1 \| a__name__isnull=True)
		# The join for a__type is created as inner join. The join is promoted
		# by a__name__isnull (ORed query => always promote isnull=True joins)

		if lookup_type == 'isnull' and value is True and not current_negated:
		promotable_joins = join_list if connector == OR else ()
		if connector == AND and can_reuse is not None:
		promotable_joins = (j for j in join_list if j not in can_reuse)
		self.promote_joins(promotable_joins)
		else:
		demotable_joins = () if connector == OR else set(join_list)
		if connector == OR and can_reuse is not None:
		demotable_joins = set(j for j in join_list if j not in can_reuse)
		for j in join_list:
		if self.alias_map[j].join_type == self.LOUTER and j in demotable_joins:
		self.alias_map[j] = self.alias_map[j]._replace(join_type=self.INNER)

		def build_filter(self, filter_expr, branch_negated=False, current_negated=False,
		can_reuse=None):
		can_reuse=None, connector=AND):
		"""
		Builds a WhereNode for a single filter clause, but doesn't add it
		to this Query. Query.add_q() will then add this filter to the where
		@@ -1139,18 +1197,14 @@ class Query(object):
		try:
		field, sources, opts, join_list, path = self.setup_joins(
		parts, opts, alias, can_reuse, allow_many,)
		if can_reuse is not None:
		can_reuse.update(join_list)
		except MultiJoin as e:
		return self.split_exclude(filter_expr, LOOKUP_SEP.join(parts[:e.level]),
		can_reuse, e.names_with_path)

		if (lookup_type == 'isnull' and value is True and not current_negated and
		len(join_list) > 1):
		# If the comparison is against NULL, we may need to use some left
		# outer joins when creating the join chain. This is only done when
		# needed, as it's less efficient at the database level.
		self.promote_joins(join_list)
		self.promote_filter_joins(join_list, can_reuse, lookup_type, value,
		current_negated, connector)
		if can_reuse is not None:
		can_reuse.update(join_list)

		# Process the join list to see if we can remove any inner joins from
		# the far end (fewer tables in a query is better). Note that join
		@@ -1182,7 +1236,7 @@ class Query(object):
		return clause

		def add_filter(self, filter_clause):
		self.where.add(self.build_filter(filter_clause), 'AND')
		self.where.add(self.build_filter(filter_clause, can_reuse=self.used_aliases), 'AND')

		def need_having(self, obj):
		"""
		@@ -1237,14 +1291,11 @@ class Query(object):
		else:
		where_part, having_parts = self.split_having_parts(
		q_object.clone(), q_object.negated)
		used_aliases = self.used_aliases
		clause = self._add_q(where_part, used_aliases)
		clause = self._add_q(where_part, self.used_aliases)
		self.where.add(clause, AND)
		for hp in having_parts:
		clause = self._add_q(hp, used_aliases)
		clause = self._add_q(hp, self.used_aliases)
		self.having.add(clause, AND)
		if self.filter_is_sticky:
		self.used_aliases = used_aliases

		def _add_q(self, q_object, used_aliases, branch_negated=False,
		current_negated=False):
		@@ -1272,7 +1323,7 @@ class Query(object):
		else:
		child_clause = self.build_filter(
		child, can_reuse=used_aliases, branch_negated=branch_negated,
		current_negated=current_negated)
		current_negated=current_negated, connector=connector)
		target_clause.add(child_clause, connector)
		if connector == OR:
		used = alias_diff(refcounts_before, self.alias_refcount)
		@@ -1445,7 +1496,7 @@ class Query(object):
		"""
		# Generate the inner query.
		query = Query(self.model)
		query.where.add(query.build_filter(filter_expr), AND)
		query.add_filter(filter_expr)
		query.clear_ordering(True)
		# Try to have as simple as possible subquery -> trim leading joins from
		# the subquery.
		@@ -1553,15 +1604,12 @@ class Query(object):

		try:
		for name in field_names:
		# Join promotion note - we must not remove any rows here, so
		# if there is no existing joins, use outer join.
		field, targets, u2, joins, path = self.setup_joins(
		name.split(LOOKUP_SEP), opts, alias, None, allow_m2m,
		True)

		# Trim last join if possible
		targets, final_alias, remaining_joins = self.trim_joins(targets, joins[-2:], path)
		joins = joins[:-2] + remaining_joins

		self.promote_joins(joins[1:])
		name.split(LOOKUP_SEP), opts, alias, can_reuse=None,
		allow_many=allow_m2m, outer_if_first=True)
		targets, final_alias, joins = self.trim_joins(targets, joins, path)
		for target in targets:
		self.select.append(SelectInfo((final_alias, target.column), target))
		except MultiJoin:

tests/aggregation_regress/models.py

+1 −1

Original line number	Diff line number	Diff line
		@@ -90,7 +90,7 @@ class HardbackBook(Book):

		# Models for ticket #21150
		class Alfa(models.Model):
		pass
		name = models.CharField(max_length=10, null=True)

		class Bravo(models.Model):
		pass

tests/aggregation_regress/tests.py

+20 −3

Original line number	Diff line number	Diff line
		@@ -12,9 +12,8 @@ from django.test import TestCase, skipUnlessDBFeature
		from django.test.utils import Approximate
		from django.utils import six

		from .models import (
		Author, Book, Publisher, Clues, Entries, HardbackBook, ItemTag,
		WithManualPK, Alfa, Bravo, Charlie)
		from .models import (Author, Book, Publisher, Clues, Entries, HardbackBook,
		ItemTag, WithManualPK, Alfa, Bravo, Charlie)


		class AggregationTests(TestCase):
		@@ -1137,6 +1136,8 @@ class AggregationTests(TestCase):
		'select__avg': Approximate(1.666, places=2),
		})


		class JoinPromotionTests(TestCase):
		def test_ticket_21150(self):
		b = Bravo.objects.create()
		c = Charlie.objects.create(bravo=b)
		@@ -1152,3 +1153,19 @@ class AggregationTests(TestCase):
		self.assertQuerysetEqual(
		qs, [c], lambda x: x)
		self.assertEqual(qs[0].alfa, a)

		def test_existing_join_not_promoted(self):
		# No promotion for existing joins
		qs = Charlie.objects.filter(alfa__name__isnull=False).annotate(Count('alfa__name'))
		self.assertTrue(' INNER JOIN ' in str(qs.query))
		# Also, the existing join is unpromoted when doing filtering for already
		# promoted join.
		qs = Charlie.objects.annotate(Count('alfa__name')).filter(alfa__name__isnull=False)
		self.assertTrue(' INNER JOIN ' in str(qs.query))
		# But, as the join is nullable first use by annotate will be LOUTER
		qs = Charlie.objects.annotate(Count('alfa__name'))
		self.assertTrue(' LEFT OUTER JOIN ' in str(qs.query))

		def test_non_nullable_fk_not_promoted(self):
		qs = Book.objects.annotate(Count('contact__name'))
		self.assertTrue(' INNER JOIN ' in str(qs.query))

tests/queries/tests.py

+33 −14

Original line number	Diff line number	Diff line
		@@ -2689,6 +2689,15 @@ class NullJoinPromotionOrTest(TestCase):
		self.assertEqual(str(qs.query).count('INNER JOIN'), 1)
		self.assertEqual(list(qs), [self.a2])

		def test_null_join_demotion(self):
		qs = ModelA.objects.filter(Q(b__name__isnull=False) & Q(b__name__isnull=True))
		self.assertTrue(' INNER JOIN ' in str(qs.query))
		qs = ModelA.objects.filter(Q(b__name__isnull=True) & Q(b__name__isnull=False))
		self.assertTrue(' INNER JOIN ' in str(qs.query))
		qs = ModelA.objects.filter(Q(b__name__isnull=False) \| Q(b__name__isnull=True))
		self.assertTrue(' LEFT OUTER JOIN ' in str(qs.query))
		qs = ModelA.objects.filter(Q(b__name__isnull=True) \| Q(b__name__isnull=False))
		self.assertTrue(' LEFT OUTER JOIN ' in str(qs.query))

		class ReverseJoinTrimmingTest(TestCase):
		def test_reverse_trimming(self):
		@@ -2785,22 +2794,19 @@ class DisjunctionPromotionTests(TestCase):
		self.assertEqual(str(qs.query).count('INNER JOIN'), 1)
		self.assertEqual(str(qs.query).count('LEFT OUTER JOIN'), 1)

		@unittest.expectedFailure
		def test_disjunction_promotion3_failing(self):
		# Now the ORed filter creates LOUTER join, but we do not have
		# logic to unpromote it for the AND filter after it. The query
		# results will be correct, but we have one LOUTER JOIN too much
		# currently.
		def test_disjunction_promotion3_demote(self):
		# This one needs demotion logic: the first filter causes a to be
		# outer joined, the second filter makes it inner join again.
		qs = BaseA.objects.filter(
		Q(a__f1='foo') \| Q(b__f2='foo')).filter(a__f2='bar')
		self.assertEqual(str(qs.query).count('INNER JOIN'), 1)
		self.assertEqual(str(qs.query).count('LEFT OUTER JOIN'), 1)

		@unittest.expectedFailure
		def test_disjunction_promotion4_failing(self):
		# Failure because no join repromotion
		def test_disjunction_promotion4_demote(self):
		qs = BaseA.objects.filter(Q(a=1) \| Q(a=2))
		self.assertEqual(str(qs.query).count('JOIN'), 0)
		# Demote needed for the "a" join. It is marked as outer join by
		# above filter (even if it is trimmed away).
		qs = qs.filter(a__f1='foo')
		self.assertEqual(str(qs.query).count('INNER JOIN'), 1)

		@@ -2810,9 +2816,8 @@ class DisjunctionPromotionTests(TestCase):
		qs = qs.filter(Q(a=1) \| Q(a=2))
		self.assertEqual(str(qs.query).count('INNER JOIN'), 1)

		@unittest.expectedFailure
		def test_disjunction_promotion5_failing(self):
		# Failure because no join repromotion logic.
		def test_disjunction_promotion5_demote(self):
		# Failure because no join demotion logic for this case.
		qs = BaseA.objects.filter(Q(a=1) \| Q(a=2))
		# Note that the above filters on a force the join to an
		# inner join even if it is trimmed.
		@@ -2823,8 +2828,8 @@ class DisjunctionPromotionTests(TestCase):
		self.assertEqual(str(qs.query).count('LEFT OUTER JOIN'), 1)
		qs = BaseA.objects.filter(Q(a__f1='foo') \| Q(b__f1='foo'))
		# Now the join to a is created as LOUTER
		self.assertEqual(str(qs.query).count('LEFT OUTER JOIN'), 0)
		qs = qs.objects.filter(Q(a=1) \| Q(a=2))
		self.assertEqual(str(qs.query).count('LEFT OUTER JOIN'), 2)
		qs = qs.filter(Q(a=1) \| Q(a=2))
		self.assertEqual(str(qs.query).count('INNER JOIN'), 1)
		self.assertEqual(str(qs.query).count('LEFT OUTER JOIN'), 1)

		@@ -3079,3 +3084,17 @@ class Ticket21203Tests(TestCase):
		qs = Ticket21203Child.objects.select_related('parent').defer('parent__created')
		self.assertQuerysetEqual(qs, [c], lambda x: x)
		self.assertIs(qs[0].parent.parent_bool, True)

		class ValuesJoinPromotionTests(TestCase):
		def test_values_no_promotion_for_existing(self):
		qs = Node.objects.filter(parent__parent__isnull=False)
		self.assertTrue(' INNER JOIN ' in str(qs.query))
		qs = qs.values('parent__parent__id')
		self.assertTrue(' INNER JOIN ' in str(qs.query))
		# Make sure there is a left outer join without the filter.
		qs = Node.objects.values('parent__parent__id')
		self.assertTrue(' LEFT OUTER JOIN ' in str(qs.query))

		def test_non_nullable_fk_not_promoted(self):
		qs = ObjectB.objects.values('objecta__name')
		self.assertTrue(' INNER JOIN ' in str(qs.query))