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Code Issues 32 Releases Wiki Activity

Fixed #33304 -- Allowed passing string expressions to Window(order_by).

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This commit is contained in:
Simon Charette
2021-11-23 00:39:04 -05:00
committed by Mariusz Felisiak
parent e06dc4571e
commit aec71aaa5b
4 changed files with 39 additions and 29 deletions
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21
django/db/models/expressions.py
View File

@@ -1333,11 +1333,13 @@ class Window(SQLiteNumericMixin, Expression):
if self.order_by is not None:
if isinstance(self.order_by, (list, tuple)):
self.order_by = ExpressionList(*self.order_by)
elif not isinstance(self.order_by, BaseExpression):
self.order_by = OrderByList(*self.order_by)
elif isinstance(self.order_by, (BaseExpression, str)):
self.order_by = OrderByList(self.order_by)
else:
raise ValueError(
'order_by must be either an Expression or a sequence of '
'expressions.'
'Window.order_by must be either a string reference to a '
'field, an expression, or a list or tuple of them.'
)
super().__init__(output_field=output_field)
self.source_expression = self._parse_expressions(expression)[0]
@@ -1363,18 +1365,17 @@ class Window(SQLiteNumericMixin, Expression):
compiler=compiler, connection=connection,
template='PARTITION BY %(expressions)s',
)
window_sql.extend(sql_expr)
window_sql.append(sql_expr)
window_params.extend(sql_params)
if self.order_by is not None:
window_sql.append(' ORDER BY ')
order_sql, order_params = compiler.compile(self.order_by)
window_sql.extend(order_sql)
window_sql.append(order_sql)
window_params.extend(order_params)
if self.frame:
frame_sql, frame_params = compiler.compile(self.frame)
window_sql.append(' ' + frame_sql)
window_sql.append(frame_sql)
window_params.extend(frame_params)
params.extend(window_params)
@@ -1382,7 +1383,7 @@ class Window(SQLiteNumericMixin, Expression):
return template % {
'expression': expr_sql,
'window': ''.join(window_sql).strip()
'window': ' '.join(window_sql).strip()
}, params
def as_sqlite(self, compiler, connection):
@@ -1399,7 +1400,7 @@ class Window(SQLiteNumericMixin, Expression):
return '{} OVER ({}{}{})'.format(
str(self.source_expression),
'PARTITION BY ' + str(self.partition_by) if self.partition_by else '',
'ORDER BY ' + str(self.order_by) if self.order_by else '',
str(self.order_by or ''),
str(self.frame or ''),
)

31
docs/ref/models/expressions.txt
View File

@@ -772,26 +772,31 @@ compute the result set.
The ``output_field`` is specified either as an argument or by the expression.
The ``order_by`` argument accepts an expression or a sequence of expressions on
which you can call :meth:`~django.db.models.Expression.asc` and
:meth:`~django.db.models.Expression.desc`. The ordering controls the order in
which the expression is applied. For example, if you sum over the rows in a
partition, the first result is the value of the first row, the second is the
sum of first and second row.
The ``order_by`` argument accepts an expression on which you can call
:meth:`~django.db.models.Expression.asc` and
:meth:`~django.db.models.Expression.desc`, a string of a field name (with an
optional ``"-"`` prefix which indicates descending order), or a tuple or list
of strings and/or expressions. The ordering controls the order in which the
expression is applied. For example, if you sum over the rows in a partition,
the first result is the value of the first row, the second is the sum of first
and second row.
The ``frame`` parameter specifies which other rows that should be used in the
computation. See :ref:`window-frames` for details.
.. versionchanged:: 4.1
Support for ``order_by`` by field name references was added.
For example, to annotate each movie with the average rating for the movies by
the same studio in the same genre and release year::
>>> from django.db.models import Avg, F, Window
>>> from django.db.models.functions import ExtractYear
>>> Movie.objects.annotate(
>>> avg_rating=Window(
>>> expression=Avg('rating'),
>>> partition_by=[F('studio'), F('genre')],
>>> order_by=ExtractYear('released').asc(),
>>> order_by='released__year',
>>> ),
>>> )
@@ -805,10 +810,9 @@ partition and ordering from the previous example is extracted into a dictionary
to reduce repetition::
>>> from django.db.models import Avg, F, Max, Min, Window
>>> from django.db.models.functions import ExtractYear
>>> window = {
>>> 'partition_by': [F('studio'), F('genre')],
>>> 'order_by': ExtractYear('released').asc(),
>>> 'order_by': 'released__year',
>>> }
>>> Movie.objects.annotate(
>>> avg_rating=Window(
@@ -887,12 +891,11 @@ same genre in the same year, this ``RowRange`` example annotates each movie
with the average rating of a movie's two prior and two following peers::
>>> from django.db.models import Avg, F, RowRange, Window
>>> from django.db.models.functions import ExtractYear
>>> Movie.objects.annotate(
>>> avg_rating=Window(
>>> expression=Avg('rating'),
>>> partition_by=[F('studio'), F('genre')],
>>> order_by=ExtractYear('released').asc(),
>>> order_by='released__year',
>>> frame=RowRange(start=-2, end=2),
>>> ),
>>> )
@@ -901,14 +904,14 @@ If the database supports it, you can specify the start and end points based on
values of an expression in the partition. If the ``released`` field of the
``Movie`` model stores the release month of each movies, this ``ValueRange``
example annotates each movie with the average rating of a movie's peers
released between twelve months before and twelve months after the each movie.
released between twelve months before and twelve months after the each movie::
>>> from django.db.models import Avg, F, ValueRange, Window
>>> Movie.objects.annotate(
>>> avg_rating=Window(
>>> expression=Avg('rating'),
>>> partition_by=[F('studio'), F('genre')],
>>> order_by=F('released').asc(),
>>> order_by='released__year',
>>> frame=ValueRange(start=-12, end=12),
>>> ),
>>> )

4
docs/releases/4.1.txt
View File

@@ -185,7 +185,9 @@ Migrations
Models
~~~~~~
* ...
* The ``order_by`` argument of the
:class:`~django.db.models.expressions.Window` expression now accepts string
references to fields and transforms.
Requests and Responses
~~~~~~~~~~~~~~~~~~~~~~

12
tests/expressions_window/tests.py
View File

@@ -51,6 +51,7 @@ class WindowFunctionTests(TestCase):
tests = [
ExtractYear(F('hire_date')).asc(),
F('hire_date__year').asc(),
'hire_date__year',
]
for order_by in tests:
with self.subTest(order_by=order_by):
@@ -473,7 +474,7 @@ class WindowFunctionTests(TestCase):
"""
qs = Employee.objects.annotate(ntile=Window(
expression=Ntile(num_buckets=4),
order_by=F('salary').desc(),
order_by='-salary',
)).order_by('ntile', '-salary', 'name')
self.assertQuerysetEqual(qs, [
('Miller', 'Management', 100000, 1),
@@ -875,7 +876,7 @@ class NonQueryWindowTests(SimpleTestCase):
)
self.assertEqual(
repr(Window(expression=Avg('salary'), order_by=F('department').asc())),
'<Window: Avg(F(salary)) OVER (ORDER BY OrderBy(F(department), descending=False))>'
'<Window: Avg(F(salary)) OVER (OrderByList(OrderBy(F(department), descending=False)))>'
)
def test_window_frame_repr(self):
@@ -942,9 +943,12 @@ class NonQueryWindowTests(SimpleTestCase):
qs.filter(equal=True)
def test_invalid_order_by(self):
msg = 'order_by must be either an Expression or a sequence of expressions'
msg = (
'Window.order_by must be either a string reference to a field, an '
'expression, or a list or tuple of them.'
)
with self.assertRaisesMessage(ValueError, msg):
Window(expression=Sum('power'), order_by='-horse')
Window(expression=Sum('power'), order_by={'-horse'})
def test_invalid_source_expression(self):
msg = "Expression 'Upper' isn't compatible with OVER clauses."