#24182: Bug with functional default and migrations
----------------------------+--------------------------------------
     Reporter:  arveitch    |                    Owner:  nobody
         Type:  Bug         |                   Status:  new
    Component:  Migrations  |                  Version:  1.7
     Severity:  Normal      |               Resolution:
     Keywords:              |             Triage Stage:  Unreviewed
    Has patch:  0           |      Needs documentation:  0
  Needs tests:  0           |  Patch needs improvement:  0
Easy pickings:  0           |                    UI/UX:  0
----------------------------+--------------------------------------
Changes (by arveitch):

 * needs_better_patch:   => 0
 * needs_tests:   => 0
 * needs_docs:   => 0


Old description:

> I've found a bug on all of 1.7; I've tested up to 1.7.3. The code works
> fine on 1.6. I think this is a reasonably common design pattern.
>
> Here's the models.py:
> {{{
> import random
> from django.db import models
>
> def generateCode(prefix=''):
>     while True:
>         code = ''.join(
>             # Omit I, O, 1 and 0 as they can cause confusion
>            random.choice('ABCDEFGHJKLMNPQRSTUVWXYZ23456789')
>            for i in range(7)
>         )
>         code = prefix + code
>         if not PromotionalCode.objects.filter(code=code).exists():
>             break
>     return code
>

> class PromotionalCode(models.Model):
>     code = models.CharField(
>         default=generateCode, db_index=True, max_length=12, unique=True
>     )
>     value_amount = models.DecimalField(
>         default=0, max_digits=7, decimal_places=2
>     )
> }}}
>
> ./manage.py migrate gives this traceback:
>
> {{{
>   Applying example.0001_initial...Traceback (most recent call last):
>   File "./manage.py", line 10, in <module>
>     execute_from_command_line(sys.argv)
>   File
> "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7
> /site-packages/django/core/management/__init__.py", line 385, in
> execute_from_command_line
>     utility.execute()
>   File
> "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7
> /site-packages/django/core/management/__init__.py", line 377, in execute
>     self.fetch_command(subcommand).run_from_argv(self.argv)
>   File
> "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7
> /site-packages/django/core/management/base.py", line 288, in
> run_from_argv
>     self.execute(*args, **options.__dict__)
>   File
> "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7
> /site-packages/django/core/management/base.py", line 338, in execute
>     output = self.handle(*args, **options)
>   File
> "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7
> /site-packages/django/core/management/commands/migrate.py", line 161, in
> handle
>     executor.migrate(targets, plan, fake=options.get("fake", False))
>   File
> "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7
> /site-packages/django/db/migrations/executor.py", line 68, in migrate
>     self.apply_migration(migration, fake=fake)
>   File
> "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7
> /site-packages/django/db/migrations/executor.py", line 102, in
> apply_migration
>     migration.apply(project_state, schema_editor)
>   File
> "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7
> /site-packages/django/db/migrations/migration.py", line 108, in apply
>     operation.database_forwards(self.app_label, schema_editor,
> project_state, new_state)
>   File
> "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7
> /site-packages/django/db/migrations/operations/models.py", line 36, in
> database_forwards
>     schema_editor.create_model(model)
>   File
> "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7
> /site-packages/django/db/backends/schema.py", line 213, in create_model
>     definition, extra_params = self.column_sql(model, field)
>   File
> "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7
> /site-packages/django/db/backends/schema.py", line 125, in column_sql
>     default_value = self.effective_default(field)
>   File
> "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7
> /site-packages/django/db/backends/schema.py", line 175, in
> effective_default
>     default = field.get_default()
>   File
> "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7
> /site-packages/django/db/models/fields/__init__.py", line 719, in
> get_default
>     return self.default()
>   File "/Users/andrew/Sites/testing/example/models.py", line 12, in
> generateCode
>     if not PromotionalCode.objects.filter(code=code).exists():
>   File
> "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7
> /site-packages/django/db/models/query.py", line 606, in exists
>     return self.query.has_results(using=self.db)
>   File
> "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7
> /site-packages/django/db/models/sql/query.py", line 457, in has_results
>     return compiler.has_results()
>   File
> "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7
> /site-packages/django/db/models/sql/compiler.py", line 757, in
> has_results
>     return bool(self.execute_sql(SINGLE))
>   File
> "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7
> /site-packages/django/db/models/sql/compiler.py", line 786, in
> execute_sql
>     cursor.execute(sql, params)
>   File
> "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7
> /site-packages/django/db/backends/utils.py", line 81, in execute
>     return super(CursorDebugWrapper, self).execute(sql, params)
>   File
> "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7
> /site-packages/django/db/backends/utils.py", line 65, in execute
>     return self.cursor.execute(sql, params)
>   File
> "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7
> /site-packages/django/db/utils.py", line 94, in __exit__
>     six.reraise(dj_exc_type, dj_exc_value, traceback)
>   File
> "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7
> /site-packages/django/db/backends/utils.py", line 65, in execute
>     return self.cursor.execute(sql, params)
>   File
> "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7
> /site-packages/django/db/backends/sqlite3/base.py", line 485, in execute
>     return Database.Cursor.execute(self, query, params)
> django.db.utils.OperationalError: no such table: example_promotionalcode
> }}}

New description:

 I've found a bug on all of 1.7; I've tested up to 1.7.3. The code works
 fine on 1.6 with syncdb. I think this is a reasonably common design
 pattern.

 Here's the models.py:
 {{{
 import random
 from django.db import models

 def generateCode(prefix=''):
     while True:
         code = ''.join(
             # Omit I, O, 1 and 0 as they can cause confusion
            random.choice('ABCDEFGHJKLMNPQRSTUVWXYZ23456789')
            for i in range(7)
         )
         code = prefix + code
         if not PromotionalCode.objects.filter(code=code).exists():
             break
     return code


 class PromotionalCode(models.Model):
     code = models.CharField(
         default=generateCode, db_index=True, max_length=12, unique=True
     )
     value_amount = models.DecimalField(
         default=0, max_digits=7, decimal_places=2
     )
 }}}

 ./manage.py migrate gives this traceback:

 {{{
   Applying example.0001_initial...Traceback (most recent call last):
   File "./manage.py", line 10, in <module>
     execute_from_command_line(sys.argv)
   File
 "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7
 /site-packages/django/core/management/__init__.py", line 385, in
 execute_from_command_line
     utility.execute()
   File
 "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7
 /site-packages/django/core/management/__init__.py", line 377, in execute
     self.fetch_command(subcommand).run_from_argv(self.argv)
   File
 "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7
 /site-packages/django/core/management/base.py", line 288, in run_from_argv
     self.execute(*args, **options.__dict__)
   File
 "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7
 /site-packages/django/core/management/base.py", line 338, in execute
     output = self.handle(*args, **options)
   File
 "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7
 /site-packages/django/core/management/commands/migrate.py", line 161, in
 handle
     executor.migrate(targets, plan, fake=options.get("fake", False))
   File
 "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7
 /site-packages/django/db/migrations/executor.py", line 68, in migrate
     self.apply_migration(migration, fake=fake)
   File
 "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7
 /site-packages/django/db/migrations/executor.py", line 102, in
 apply_migration
     migration.apply(project_state, schema_editor)
   File
 "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7
 /site-packages/django/db/migrations/migration.py", line 108, in apply
     operation.database_forwards(self.app_label, schema_editor,
 project_state, new_state)
   File
 "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7
 /site-packages/django/db/migrations/operations/models.py", line 36, in
 database_forwards
     schema_editor.create_model(model)
   File
 "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7
 /site-packages/django/db/backends/schema.py", line 213, in create_model
     definition, extra_params = self.column_sql(model, field)
   File
 "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7
 /site-packages/django/db/backends/schema.py", line 125, in column_sql
     default_value = self.effective_default(field)
   File
 "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7
 /site-packages/django/db/backends/schema.py", line 175, in
 effective_default
     default = field.get_default()
   File
 "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7
 /site-packages/django/db/models/fields/__init__.py", line 719, in
 get_default
     return self.default()
   File "/Users/andrew/Sites/testing/example/models.py", line 12, in
 generateCode
     if not PromotionalCode.objects.filter(code=code).exists():
   File
 "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7
 /site-packages/django/db/models/query.py", line 606, in exists
     return self.query.has_results(using=self.db)
   File
 "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7
 /site-packages/django/db/models/sql/query.py", line 457, in has_results
     return compiler.has_results()
   File
 "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7
 /site-packages/django/db/models/sql/compiler.py", line 757, in has_results
     return bool(self.execute_sql(SINGLE))
   File
 "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7
 /site-packages/django/db/models/sql/compiler.py", line 786, in execute_sql
     cursor.execute(sql, params)
   File
 "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7
 /site-packages/django/db/backends/utils.py", line 81, in execute
     return super(CursorDebugWrapper, self).execute(sql, params)
   File
 "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7
 /site-packages/django/db/backends/utils.py", line 65, in execute
     return self.cursor.execute(sql, params)
   File
 "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7
 /site-packages/django/db/utils.py", line 94, in __exit__
     six.reraise(dj_exc_type, dj_exc_value, traceback)
   File
 "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7
 /site-packages/django/db/backends/utils.py", line 65, in execute
     return self.cursor.execute(sql, params)
   File
 "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7
 /site-packages/django/db/backends/sqlite3/base.py", line 485, in execute
     return Database.Cursor.execute(self, query, params)
 django.db.utils.OperationalError: no such table: example_promotionalcode
 }}}

 If I comment out the PromotionalCode.objects.filter(code=code).exists()
 test then it works fine on 1.7

--

--
Ticket URL: <https://code.djangoproject.com/ticket/24182#comment:1>
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