I am try to conver from numberic to string a result of annotated field
(created by a annotation).
I am wrote my Func as next:
class ToStr(Func):
"""
"""
function = 'CAST'
template = '%(function)s(%(expressions)s as TEXT)'
class ToChar(Func):
"""
"""
function = 'CAST'
template = '%(function)s(%(expressions)s as VARCHAR)'
I have next code for queryset of model:
class SolutionQuerySet(models.QuerySet):
"""
QuerySet for solutions.
"""
def solutions_with_scopes(self):
"""Added for each solution new field 'scope' where storage her
scope."""
self = self.annotate(scope=models.Sum(
models.Case(
models.When(opinions__is_useful=True, then=1),
models.When(opinions__is_useful=False, then=-1),
output_field=models.IntegerField()
)
))
self = self.annotate(scope=models.functions.Coalesce('scope', 0))
return self
def solutions_with_displayed_scopes(self):
"""Convert scope of solution to string and return with sign of
number:
if 0 return 0, if 1 return +1, if -1 return -1."""
self = self.solutions_with_scopes()
self = self.annotate(s=ToStr('scope'))
self = self.annotate(s1=ToChar('scope'))
# self = self.annotate(displayed_scope=models.Case(
# models.When(scope__exact=0, then=models.Value('0')),
# models.When(scope__lt=0, then=models.Value('-')),
# models.When(scope__gt=0, then=models.Value('+')),
# output_field=models.CharField(),
# ))
return self
This converting working with SlugField and UUIDField, however not with
IntegerField (created by annotate()):
*Worked with SlugField:*
def solutions_with_displayed_scopes(self):
"""Convert scope of solution to string and return with sign of
number:
if 0 return 0, if 1 return +1, if -1 return -1."""
self = self.solutions_with_scopes()
self = self.annotate(s=ToStr('slug'))
self = self.annotate(s1=ToChar('slug'))
In [2]: Solution.objects.solutions_with_displayed_scopes().values('s',
> 's1')[0]
> Out[2]: {'s': 'how-fix-problem-on-heroku', 's1':
> 'how-fix-problem-on-heroku'}
*Worked with UUIDField:*
def solutions_with_displayed_scopes(self):
"""Convert scope of solution to string and return with sign of
number:
if 0 return 0, if 1 return +1, if -1 return -1."""
self = self.solutions_with_scopes()
self = self.annotate(s=ToStr('id'))
self = self.annotate(s1=ToChar('id'))
In [1]: Solution.objects.solutions_with_displayed_scopes().values('s',
> 's1')[0]
> Out[1]:
> {'s': '9f9beadd-be37-4475-9e11-890172987f80',
> 's1': '9f9beadd-be37-4475-9e11-890172987f80'}
*Not worked with IntegerField:*
def solutions_with_displayed_scopes(self):
"""Convert scope of solution to string and return with sign of
number:
if 0 return 0, if 1 return +1, if -1 return -1."""
self = self.solutions_with_scopes()
self = self.annotate(s=ToStr('scope'))
self = self.annotate(s1=ToChar('scope'))
In [1]: Solution.objects.solutions_with_displayed_scopes().values('s',
> 's1')[0]
> Out[1]: {'s': -2, 's1': -2}
Must be:
In [1]: Solution.objects.solutions_with_displayed_scopes().values('s',
> 's1')[0]
> Out[1]: {'s': '-2', 's1': '-2'}
Can anyone explain, why Postgres have this behaivor?
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