django中的makemigrations是否因爲某種原因重新創建現有的表？

Question

我想驗證django 1.8中是否存在使用sql lite進行makemigrations的錯誤，或者我做錯了什麼。

1. 我刪除了我的數據庫並刪除了所有遷移文件夾。我跑

python manage.py makemigrations 
python manage.py migrate 

DB被創建沒有問題。

2.我必須修改現有模式在應用程序中的一個（應用ABC） 我執行我的變化，然後再次運行

python manage.py makemigrations 

3.it沒有發現任何變化

然後我再次運行同樣的事情，但隨着應用程序的名稱

python manage.py makemigrations abc 

4.它在遷移時做了一些更新，我相信它會重新創建所有表格，而不僅僅是我的變化!!!!

5.Then我執行

python manage.py migrate

並得到錯誤的表已經存在。

這是在Django框架中的錯誤，或者我做錯了什麼，並有一個原因，爲什麼它的行爲是這樣嗎？

從我的外殼複製粘貼從第2步開始：

(mrp) C:\Users\I812624\dev\mrp\src>python manage.py makemigrations 
No changes detected 

(mrp) C:\Users\I812624\dev\mrp\src>python manage.py makemigrations purchase 
Migrations for 'purchase': 
    0001_initial.py: 
    - Create model PO 
    - Create model POmaterial 

(mrp) C:\Users\I812624\dev\mrp\src>python manage.py migrate 
Operations to perform: 
    Synchronize unmigrated apps: customer, manufacture, product, django_filters, a 
utofixture, staticfiles, messages, smart_selects, watson, sales, item, django_co 
untries, mptt, inventory, django_select2, production, main, crispy_forms 
    Apply all migrations: purchase, vendor, sessions, admin, sites, flatpages, con 
tenttypes, auth, registration 
Synchronizing apps without migrations: 
    Creating tables... 
    Running deferred SQL... 
    Installing custom SQL... 
Running migrations: 
    Rendering model states... DONE 
    Applying purchase.0001_initial...Traceback (most recent call last): 
    File "manage.py", line 10, in <module> 
    execute_from_command_line(sys.argv) 
    File "C:\Users\I812624\dev\mrp\lib\site-packages\django\core\management\__init 
__.py", line 338, in execute_from_command_line 
    utility.execute() 
    File "C:\Users\I812624\dev\mrp\lib\site-packages\django\core\management\__init 
__.py", line 330, in execute 
    self.fetch_command(subcommand).run_from_argv(self.argv) 
    File "C:\Users\I812624\dev\mrp\lib\site-packages\django\core\management\base.p 
y", line 390, in run_from_argv 
    self.execute(*args, **cmd_options) 
    File "C:\Users\I812624\dev\mrp\lib\site-packages\django\core\management\base.p 
y", line 441, in execute 
    output = self.handle(*args, **options) 
    File "C:\Users\I812624\dev\mrp\lib\site-packages\django\core\management\comman 
ds\migrate.py", line 221, in handle 
    executor.migrate(targets, plan, fake=fake, fake_initial=fake_initial) 
    File "C:\Users\I812624\dev\mrp\lib\site-packages\django\db\migrations\executor 
.py", line 110, in migrate 
    self.apply_migration(states[migration], migration, fake=fake, fake_initial=f 
ake_initial) 
    File "C:\Users\I812624\dev\mrp\lib\site-packages\django\db\migrations\executor 
.py", line 147, in apply_migration 
    state = migration.apply(state, schema_editor) 
    File "C:\Users\I812624\dev\mrp\lib\site-packages\django\db\migrations\migratio 
n.py", line 115, in apply 
    operation.database_forwards(self.app_label, schema_editor, old_state, projec 
t_state) 
    File "C:\Users\I812624\dev\mrp\lib\site-packages\django\db\migrations\operatio 
ns\models.py", line 59, in database_forwards 
    schema_editor.create_model(model) 
    File "C:\Users\I812624\dev\mrp\lib\site-packages\django\db\backends\base\schem 
a.py", line 282, in create_model 
    self.execute(sql, params or None) 
    File "C:\Users\I812624\dev\mrp\lib\site-packages\django\db\backends\base\schem 
a.py", line 107, in execute 
    cursor.execute(sql, params) 
    File "C:\Users\I812624\dev\mrp\lib\site-packages\django\db\backends\utils.py", 
line 79, in execute 
    return super(CursorDebugWrapper, self).execute(sql, params) 
    File "C:\Users\I812624\dev\mrp\lib\site-packages\django\db\backends\utils.py", 
line 64, in execute 
    return self.cursor.execute(sql, params) 
    File "C:\Users\I812624\dev\mrp\lib\site-packages\django\db\utils.py", line 97, 
in __exit__ 
    six.reraise(dj_exc_type, dj_exc_value, traceback) 
    File "C:\Users\I812624\dev\mrp\lib\site-packages\django\db\backends\utils.py", 
line 62, in execute 
    return self.cursor.execute(sql) 
    File "C:\Users\I812624\dev\mrp\lib\site-packages\django\db\backends\sqlite3\ba 
se.py", line 316, in execute 
    return Database.Cursor.execute(self, query) 
django.db.utils.OperationalError: table "purchase_po" already exists 

Answer 1

要回答我的問題。

所以我想通了。我認爲問題在於我最初刪除了文件夾遷移，而當我運行makemigrations時未指定特定的應用程序，它確實創建了一個數據庫，但它已經創建了包含____init____.py的文件夾makemigrations。

解決方案每當你刪除數據庫和刪除migrations文件夾不管是什麼原因不刪除遷移文件夾，但只有其內容不包括init文件。 或者當您確實刪除文件夾時，運行爲@MicroPyramid建議的每個應用程序單獨進行遷移。

沒有做更深入的調查，它在我看來或是作爲令人困惑的設計行爲或來自Django方面的錯誤。