I am managing a django app built by third parts.
I have configured in settings.py the connection to a new db
'default': { # changed
'ENGINE': 'django.contrib.gis.db.backends.postgis',
'NAME': 'waterwatch',
'USER': 'waterwatch_main',
'PASSWORD': '****',
'HOST': 'localhost',
}
Now I want to populate the new database with the table in my models.py, that is
class WaterConsumption(models.Model):
Id = models.IntegerField(primary_key=True)
Suburb = models.CharField(max_length=100)
NoOfSingleResProp = models.IntegerField()
AvgMonthlyKL = models.IntegerField()
AvgMonthlyKLPredicted = models.IntegerField()
PredictionAccuracy = models.IntegerField()
Month = models.CharField(max_length=50)
Year = models.IntegerField()
DateTime = models.DateTimeField()
geom = models.PointField()
def __str__(self):
return self.Suburb
class Meta:
verbose_name_plural = 'WaterConsumption'
so I run
python manage.py makemigrations
but I get
django.db.utils.ProgrammingError: relation "waterwatchapp_waterconsumption" does not exist
well... I guess that is obvious, I am actually trying to create new tables in my new database.
I guess something is wrong with the migrations.
so I have dropped and recreated the database, deleted all files in
waterwatchapp/migrations , except __init__.py
waterwatchapp/__pycache__
waterwatch/__pycache__
But as I run again python manage.py makemigrations or python manage.py migrate, I still get the same error.
Why does django does not creates the tables anew?
It seems to me that django is still somehow following a sort of track of what was in the database before.
How can I remove all the migration history done before, and make django apply the migrations to a new database? (I don't care about the stored data)
Complete traceback.
Watching for file changes with StatReloader
Exception in thread django-main-thread:
Traceback (most recent call last):
File "/home/tommaso/tommaso03/coding_projects/corsi_udemy/create-smart-maps-in-python-and-leaflet/waterwatch/venv/lib/python3.10/site-packages/django/db/backends/utils.py", line 85, in _execute
return self.cursor.execute(sql, params)
psycopg2.errors.UndefinedTable: relation "waterwatchapp_waterconsumption" does not exist
LINE 1: UPDATE "waterwatchapp_waterconsumption" SET "Suburb" = 'ATHL...
^
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
File "/usr/lib/python3.10/threading.py", line 1016, in _bootstrap_inner
self.run()
File "/usr/lib/python3.10/threading.py", line 953, in run
self._target(*self._args, **self._kwargs)
File "/home/tommaso/tommaso03/coding_projects/corsi_udemy/create-smart-maps-in-python-and-leaflet/waterwatch/venv/lib/python3.10/site-packages/django/utils/autoreload.py", line 64, in wrapper
fn(*args, **kwargs)
File "/home/tommaso/tommaso03/coding_projects/corsi_udemy/create-smart-maps-in-python-and-leaflet/waterwatch/venv/lib/python3.10/site-packages/django/core/management/commands/runserver.py", line 115, in inner_run
autoreload.raise_last_exception()
File "/home/tommaso/tommaso03/coding_projects/corsi_udemy/create-smart-maps-in-python-and-leaflet/waterwatch/venv/lib/python3.10/site-packages/django/utils/autoreload.py", line 87, in raise_last_exception
raise _exception[1]
File "/home/tommaso/tommaso03/coding_projects/corsi_udemy/create-smart-maps-in-python-and-leaflet/waterwatch/venv/lib/python3.10/site-packages/django/core/management/__init__.py", line 381, in execute
autoreload.check_errors(django.setup)()
File "/home/tommaso/tommaso03/coding_projects/corsi_udemy/create-smart-maps-in-python-and-leaflet/waterwatch/venv/lib/python3.10/site-packages/django/utils/autoreload.py", line 64, in wrapper
fn(*args, **kwargs)
File "/home/tommaso/tommaso03/coding_projects/corsi_udemy/create-smart-maps-in-python-and-leaflet/waterwatch/venv/lib/python3.10/site-packages/django/__init__.py", line 24, in setup
apps.populate(settings.INSTALLED_APPS)
File "/home/tommaso/tommaso03/coding_projects/corsi_udemy/create-smart-maps-in-python-and-leaflet/waterwatch/venv/lib/python3.10/site-packages/django/apps/registry.py", line 122, in populate
app_config.ready()
File "/home/tommaso/tommaso03/coding_projects/corsi_udemy/create-smart-maps-in-python-and-leaflet/waterwatch/venv/lib/python3.10/site-packages/django/contrib/admin/apps.py", line 27, in ready
self.module.autodiscover()
File "/home/tommaso/tommaso03/coding_projects/corsi_udemy/create-smart-maps-in-python-and-leaflet/waterwatch/venv/lib/python3.10/site-packages/django/contrib/admin/__init__.py", line 24, in autodiscover
autodiscover_modules('admin', register_to=site)
File "/home/tommaso/tommaso03/coding_projects/corsi_udemy/create-smart-maps-in-python-and-leaflet/waterwatch/venv/lib/python3.10/site-packages/django/utils/module_loading.py", line 57, in autodiscover_modules
import_module('%s.%s' % (app_config.name, module_to_search))
File "/usr/lib/python3.10/importlib/__init__.py", line 126, in import_module
return _bootstrap._gcd_import(name[level:], package, level)
File "<frozen importlib._bootstrap>", line 1050, in _gcd_import
File "<frozen importlib._bootstrap>", line 1027, in _find_and_load
File "<frozen importlib._bootstrap>", line 1006, in _find_and_load_unlocked
File "<frozen importlib._bootstrap>", line 688, in _load_unlocked
File "<frozen importlib._bootstrap_external>", line 883, in exec_module
File "<frozen importlib._bootstrap>", line 241, in _call_with_frames_removed
File "/home/tommaso/tommaso03/coding_projects/corsi_udemy/create-smart-maps-in-python-and-leaflet/waterwatch/waterwatchapp/admin.py", line 44, in <module>
).save()
File "/home/tommaso/tommaso03/coding_projects/corsi_udemy/create-smart-maps-in-python-and-leaflet/waterwatch/venv/lib/python3.10/site-packages/django/db/models/base.py", line 743, in save
self.save_base(using=using, force_insert=force_insert,
File "/home/tommaso/tommaso03/coding_projects/corsi_udemy/create-smart-maps-in-python-and-leaflet/waterwatch/venv/lib/python3.10/site-packages/django/db/models/base.py", line 780, in save_base
updated = self._save_table(
File "/home/tommaso/tommaso03/coding_projects/corsi_udemy/create-smart-maps-in-python-and-leaflet/waterwatch/venv/lib/python3.10/site-packages/django/db/models/base.py", line 862, in _save_table
updated = self._do_update(base_qs, using, pk_val, values, update_fields,
File "/home/tommaso/tommaso03/coding_projects/corsi_udemy/create-smart-maps-in-python-and-leaflet/waterwatch/venv/lib/python3.10/site-packages/django/db/models/base.py", line 916, in _do_update
return filtered._update(values) > 0
File "/home/tommaso/tommaso03/coding_projects/corsi_udemy/create-smart-maps-in-python-and-leaflet/waterwatch/venv/lib/python3.10/site-packages/django/db/models/query.py", line 809, in _update
return query.get_compiler(self.db).execute_sql(CURSOR)
File "/home/tommaso/tommaso03/coding_projects/corsi_udemy/create-smart-maps-in-python-and-leaflet/waterwatch/venv/lib/python3.10/site-packages/django/db/models/sql/compiler.py", line 1591, in execute_sql
cursor = super().execute_sql(result_type)
File "/home/tommaso/tommaso03/coding_projects/corsi_udemy/create-smart-maps-in-python-and-leaflet/waterwatch/venv/lib/python3.10/site-packages/django/db/models/sql/compiler.py", line 1202, in execute_sql
cursor.execute(sql, params)
File "/home/tommaso/tommaso03/coding_projects/corsi_udemy/create-smart-maps-in-python-and-leaflet/waterwatch/venv/lib/python3.10/site-packages/django/db/backends/utils.py", line 99, in execute
return super().execute(sql, params)
File "/home/tommaso/tommaso03/coding_projects/corsi_udemy/create-smart-maps-in-python-and-leaflet/waterwatch/venv/lib/python3.10/site-packages/django/db/backends/utils.py", line 67, in execute
return self._execute_with_wrappers(sql, params, many=False, executor=self._execute)
File "/home/tommaso/tommaso03/coding_projects/corsi_udemy/create-smart-maps-in-python-and-leaflet/waterwatch/venv/lib/python3.10/site-packages/django/db/backends/utils.py", line 76, in _execute_with_wrappers
return executor(sql, params, many, context)
File "/home/tommaso/tommaso03/coding_projects/corsi_udemy/create-smart-maps-in-python-and-leaflet/waterwatch/venv/lib/python3.10/site-packages/django/db/backends/utils.py", line 80, in _execute
with self.db.wrap_database_errors:
File "/home/tommaso/tommaso03/coding_projects/corsi_udemy/create-smart-maps-in-python-and-leaflet/waterwatch/venv/lib/python3.10/site-packages/django/db/utils.py", line 90, in __exit__
raise dj_exc_value.with_traceback(traceback) from exc_value
File "/home/tommaso/tommaso03/coding_projects/corsi_udemy/create-smart-maps-in-python-and-leaflet/waterwatch/venv/lib/python3.10/site-packages/django/db/backends/utils.py", line 85, in _execute
return self.cursor.execute(sql, params)
django.db.utils.ProgrammingError: relation "waterwatchapp_waterconsumption" does not exist
LINE 1: UPDATE "waterwatchapp_waterconsumption" SET "Suburb" = 'ATHL...
By looking deeper into the Traceback, I noticed this snippet
File "/home/tommaso/tommaso03/coding_projects/corsi_udemy/create-smart-maps-in-python-and-leaflet/waterwatch/venv/lib/python3.10/site-packages/django/contrib/admin/__init__.py", line 24, in autodiscover
autodiscover_modules('admin', register_to=site)
This made me think django tryed to access the table before it was created, raising the error.
This was actually done by waterwatchapp/admin.py.
# Register your models here.
class WaterConsumptionAdmin(LeafletGeoAdmin):
pass
admin.site.register(WaterConsumption, WaterConsumptionAdmin)
df_excelReader = pd.read_excel(BASE_DIR / 'tabledata_source/waterwatch_clean2.xlsx')
for index, row in df_excelReader.iterrows():
Id = index
Suburb = row['Suburb']
NoOfSingleResProp = row['Number of single-residential properties_number']
AvgMonthlyKL = row['Oct 2017\nkl/month']
AvgMonthlyKLPredicted = 0
PredictionAccuracy = 0
Month = row ['Month']
Year = row['Year']
DateTime = datetime.now()
Longitude = row['Longitude']
Latitude = row['Latitude']
WaterConsumption(Id=Id,
Suburb=Suburb,
NoOfSingleResProp=NoOfSingleResProp,
AvgMonthlyKL=AvgMonthlyKL,
AvgMonthlyKLPredicted=AvgMonthlyKLPredicted,
PredictionAccuracy=PredictionAccuracy,
Month=Month,
Year=Year,
DateTime=DateTime,
geom=Point(Longitude, Latitude)
).save()
I commented all the lines of code of waterwatchapp/admin.py involving the table quoted by the traceback (WaterConsumption, in the traceback it is like djangoapp_djangomodel, all lowercase), then I run
python manage.py makemigrations
and it worked!
Then I decommented the lines.
Also, a simple try-except structure could do the job.
try:
# Register your models here.
class WaterConsumptionAdmin(LeafletGeoAdmin):
pass
admin.site.register(WaterConsumption, WaterConsumptionAdmin)
df_excelReader = pd.read_excel(BASE_DIR / 'tabledata_source/waterwatch_clean2.xlsx')
for index, row in df_excelReader.iterrows():
Id = index
Suburb = row['Suburb']
NoOfSingleResProp = row['Number of single-residential properties_number']
AvgMonthlyKL = row['Oct 2017\nkl/month']
AvgMonthlyKLPredicted = 0
PredictionAccuracy = 0
Month = row ['Month']
Year = row['Year']
DateTime = datetime.now()
Longitude = row['Longitude']
Latitude = row['Latitude']
WaterConsumption(Id=Id,
Suburb=Suburb,
NoOfSingleResProp=NoOfSingleResProp,
AvgMonthlyKL=AvgMonthlyKL,
AvgMonthlyKLPredicted=AvgMonthlyKLPredicted,
PredictionAccuracy=PredictionAccuracy,
Month=Month,
Year=Year,
DateTime=DateTime,
geom=Point(Longitude, Latitude)
).save()
except Exception:
print(traceback.format_exc())
print("Cannot access table WaterConsumption.")
furthermore, I have found a quite unelegant way to avoid the error to be raised:
I have added a snippet that accesses the table only if the table already exists.
# introducing a condition, to avoid django access the table when it is not created yet
from django.db import connection
all_tables = connection.introspection.table_names()
table_name = 'waterwatchapp' + '_' + 'WaterConsumption'.lower()
if table_name in all_tables:
# Register your models here.
class WaterConsumptionAdmin(LeafletGeoAdmin):
pass
admin.site.register(WaterConsumption, WaterConsumptionAdmin)
for index, row in df_excelReader.iterrows():
Id = index
Suburb = row['Suburb']
NoOfSingleResProp = row['Number of single-residential properties_number']
AvgMonthlyKL = row['Oct 2017\nkl/month']
AvgMonthlyKLPredicted = 0
PredictionAccuracy = 0
Month = row ['Month']
Year = row['Year']
DateTime = datetime.now()
Longitude = row['Longitude']
Latitude = row['Latitude']
WaterConsumption(Id=Id,
Suburb=Suburb,
NoOfSingleResProp=NoOfSingleResProp,
AvgMonthlyKL=AvgMonthlyKL,
AvgMonthlyKLPredicted=AvgMonthlyKLPredicted,
PredictionAccuracy=PredictionAccuracy,
Month=Month,
Year=Year,
DateTime=DateTime,
geom=Point(Longitude, Latitude)
).save()