django.db.utils.IntegrityError: UNIQUE constraint failed

Question

Hi m new in django framework and I am trying to solve this problem from 2 day I am getting this error after python manage.py migrate command. I cant understand what the problem is?

models.py

from django.db import models
from django.utils import timezone


class BlogPost(models.Model):
    author = models.ForeignKey('auth.User')
    title = models.CharField(max_length=100,unique=True)
    text = models.TextField()
    created_date = models.DateTimeField(default=timezone.now)
    published_date = models.DateTimeField(blank=True,null=True)

def publish(self):
    self.published_date=timezone.now()
    self.save()

def __str__(self):
    return self.title

error

  File "/home/letsperf/.conda/envs/MyDjangoEnv/lib/python3.5/site-packages   /django/db/migrations/migration.py", line 129, in apply
operation.database_forwards(self.app_label, schema_editor, old_state, project_state)
  File "/home/letsperf/.conda/envs/MyDjangoEnv/lib/python3.5/site-packages/django/db/migrations/operations/fields.py", line 216, in database_forwards
schema_editor.alter_field(from_model, from_field, to_field)
  File "/home/letsperf/.conda/envs/MyDjangoEnv/lib/python3.5/site-packages/django/db/backends/base/schema.py", line 515, in alter_field
old_db_params, new_db_params, strict)
  File "/home/letsperf/.conda/envs/MyDjangoEnv/lib/python3.5/site-packages/django/db/backends/sqlite3/schema.py", line 262, in _alter_field
self._remake_table(model, alter_field=(old_field, new_field))
  File "/home/letsperf/.conda/envs/MyDjangoEnv/lib/python3.5/site-packages/django/db/backends/sqlite3/schema.py", line 206, in _remake_table
self.quote_name(model._meta.db_table),
  File "/home/letsperf/.conda/envs/MyDjangoEnv/lib/python3.5/site-packages/django/db/backends/base/schema.py", line 120, in execute
cursor.execute(sql, params)
  File "/home/letsperf/.conda/envs/MyDjangoEnv/lib/python3.5/site-packages/django/db/backends/utils.py", line 80, in execute
return super(CursorDebugWrapper, self).execute(sql, params)
  File "/home/letsperf/.conda/envs/MyDjangoEnv/lib/python3.5/site-packages/django/db/backends/utils.py", line 65, in execute
return self.cursor.execute(sql, params)
  File "/home/letsperf/.conda/envs/MyDjangoEnv/lib/python3.5/site-packages/django/db/utils.py", line 94, in __exit__
six.reraise(dj_exc_type, dj_exc_value, traceback)
  File "/home/letsperf/.conda/envs/MyDjangoEnv/lib/python3.5/site-packages/django/utils/six.py", line 685, in reraise
raise value.with_traceback(tb)
  File "/home/letsperf/.conda/envs/MyDjangoEnv/lib/python3.5/site-packages/django/db/backends/utils.py", line 65, in execute
return self.cursor.execute(sql, params)
  File "/home/letsperf/.conda/envs/MyDjangoEnv/lib/python3.5/site-packages/django/db/backends/sqlite3/base.py", line 328, in execute
return Database.Cursor.execute(self, query, params)
django.db.utils.IntegrityError: UNIQUE constraint failed: social_blogpost.title

please help I am confused !!

The error is clearly straight to the point. You have defined title as unique and Django won't let you save same value twice for a unique field. — zaidfazil
– zaidfazil, Commented Jul 21, 2017 at 10:34
What were you trying to do? If you don't want that unique constraint you can remove it — zaidfazil
– zaidfazil, Commented Jul 21, 2017 at 11:08
i want title should be unique no one can use it again , Is there any other method you know ? — Dexter
– Dexter, Commented Jul 21, 2017 at 11:13
You already have an object with the same title in the database. Delete it or edit it. — zaidfazil
– zaidfazil, Commented Jul 21, 2017 at 11:14

Toluwalemi · Accepted Answer · 2019-06-04 14:56:37Z

3

According to Django documentation, this is a summary of what the problem is;

Applying a “plain” migration that adds a unique non-nullable field to a table with existing rows will raise an error because the value used to populate existing rows is generated only once, thus breaking the unique constraint.

answered Jun 4, 2019 at 14:56

Toluwalemi

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