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from django.db.models import Value as V
from django.db.models.functions import Lower, StrIndex, Substr, Upper
from django.test import TestCase
from ..models import Author
class SubstrTests(TestCase):
def test_basic(self):
Author.objects.create(name="John Smith", alias="smithj")
Author.objects.create(name="Rhonda")
authors = Author.objects.annotate(name_part=Substr("name", 5, 3))
self.assertQuerySetEqual(
authors.order_by("name"), [" Sm", "da"], lambda a: a.name_part
)
authors = Author.objects.annotate(name_part=Substr("name", 2))
self.assertQuerySetEqual(
authors.order_by("name"), ["ohn Smith", "honda"], lambda a: a.name_part
)
# If alias is null, set to first 5 lower characters of the name.
Author.objects.filter(alias__isnull=True).update(
alias=Lower(Substr("name", 1, 5)),
)
self.assertQuerySetEqual(
authors.order_by("name"), ["smithj", "rhond"], lambda a: a.alias
)
def test_start(self):
Author.objects.create(name="John Smith", alias="smithj")
a = Author.objects.annotate(
name_part_1=Substr("name", 1),
name_part_2=Substr("name", 2),
).get(alias="smithj")
self.assertEqual(a.name_part_1[1:], a.name_part_2)
def test_pos_gt_zero(self):
with self.assertRaisesMessage(ValueError, "'pos' must be greater than 0"):
Author.objects.annotate(raises=Substr("name", 0))
def test_expressions(self):
Author.objects.create(name="John Smith", alias="smithj")
Author.objects.create(name="Rhonda")
substr = Substr(Upper("name"), StrIndex("name", V("h")), 5)
authors = Author.objects.annotate(name_part=substr)
self.assertQuerySetEqual(
authors.order_by("name"), ["HN SM", "HONDA"], lambda a: a.name_part
)
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