Opened 11 years ago

Last modified 6 years ago

#12529 new Bug syncdb doesn't check tables by using mangled names with Oracle backend

Reported by: Jani Tiainen Owned by: nobody
Component: Database layer (models, ORM) Version: master
Severity: Normal Keywords: syncdb oracle inspectdb
Cc: Triage Stage: Accepted
Has patch: no Needs documentation: no
Needs tests: no Patch needs improvement: no
Easy pickings: no UI/UX: no


With Oracle syncdb doesn't use mangled names when comparing tablenames to ones existing in database thus trying to create tables that already exists. This leads to

Creating table ssp_service_category_translation
Traceback (most recent call last):
  File "./", line 19, in <module>
  File "../../django-trunk/django/core/management/", line 439, in execute_manager
  File "../../django-trunk/django/core/management/", line 380, in execute
  File "../../django-trunk/django/core/management/", line 195, in run_from_argv
    self.execute(*args, **options.__dict__)
  File "../../django-trunk/django/core/management/", line 222, in execute
    output = self.handle(*args, **options)
  File "../../django-trunk/django/core/management/", line 351, in handle
    return self.handle_noargs(**options)
  File "../../django-trunk/django/core/management/commands/", line 91, in handle_noargs
  File "../../django-trunk/django/db/backends/", line 19, in execute
    return self.cursor.execute(sql, params)
  File "../../django-trunk/django/db/backends/oracle/", line 487, in execute
    raise e
cx_Oracle.DatabaseError: ORA-00955: name is already used by an existing object

Root cause for this is using connection.introspection.table_name_converter() in syncdb main loop which in case of oracle returns just lowercase name and not properly mangled name that would match existing table in database.

Change History (10)

comment:1 Changed 11 years ago by Jani Tiainen

This happens only when model has db_table defined in Meta:

class ThisIsLongModelThatDoesNotFail(models.Model):

class ThisFails(models.Model):
    class Meta:
        db_table = 'very_long_table_name_that_will_fail'

Note: This also happens in pre-multidb codebase.

comment:2 Changed 11 years ago by Jani Tiainen

It seems that django/db/models/ around L105 uses tablename truncate only when table name is not provided.

I think truncate should happen regardless is it provided or not to make models work regardless of DB.

Currently this only is Oracle problem since it's only db backend that has limitation on names.

comment:3 Changed 11 years ago by Russell Keith-Magee

Triage Stage: UnreviewedAccepted

comment:4 Changed 10 years ago by Thejaswi Puthraya

Component: UncategorizedDatabase layer (models, ORM)

comment:5 Changed 9 years ago by Matt McClanahan

Severity: Normal
Type: Bug

comment:6 Changed 9 years ago by Ramiro Morales

Easy pickings: unset
Keywords: inspectdb added
UI/UX: unset

comment:7 Changed 7 years ago by manelclos@…

Hi, I've fixed this by changing


    def table_name_converter(self, name):
        "Table name comparison is case insensitive under Oracle"
        return name.lower()


from django.db.backends import util
    def table_name_converter(self, name):
        "Table name comparison is case insensitive under Oracle"
        max_length = self.connection.ops.max_name_length()
        truncated = util.truncate_name(name.upper(), max_length)
        return truncated.lower()

Is there any problem in this solution?

comment:8 Changed 6 years ago by Aymeric Augustin

Resolution: fixed
Status: newclosed

With the introduction of the new migrations framework in Django 1.7, this issue doesn't exist anymore.

comment:9 Changed 6 years ago by Manel Clos

Hi, I can still reproduce this using Django 1.7 and 1.7.1.

As an example, let's use django-cas' table "django_cas_session_service_ticket". This also happens with easy_thumbails' table "easy_thumbnails_thumbnaildimensions".

The flow is like this:

  • migrate command is called, eventually is called:
            def model_installed(model):
                opts = model._meta
                converter = connection.introspection.table_name_converter
                # Note that if a model is unmanaged we short-circuit and never try to install it
                return not ((converter(opts.db_table) in tables) or
                    (opts.auto_created and converter(opts.auto_created._meta.db_table) in tables))
  • here, the table name converter will just return name.lower(), which is clearly NOT the name that was used to create the table.
  • at creation time, the Oracle DatabaseOperations (oracle/ class will truncate the name:
    def quote_name(self, name):
        # SQL92 requires delimited (quoted) names to be case-sensitive.  When
        # not quoted, Oracle has case-insensitive behavior for identifiers, but
        # always defaults to uppercase.
        # We simplify things by making Oracle identifiers always uppercase.
        if not name.startswith('"') and not name.endswith('"'):
            name = '"%s"' % backend_utils.truncate_name(name.upper(),
        # Oracle puts the query text into a (query % args) construct, so % signs
        # in names need to be escaped. The '%%' will be collapsed back to '%' at
        # that stage so we aren't really making the name longer here.
        name = name.replace('%', '%%')
        return name.upper()
  • the check for table existance "(converter(opts.db_table) in tables)" will fail, as tables array contains "django_cas_session_service1144" and not "django_cas_session_service_ticket"
  • with these changes in oracle/ everything works as expected. imports included in function for easier testing:
    def table_name_converter(self, name):
        "Table name comparison is case insensitive under Oracle"
        from django.db.backends import utils as backend_utils
        from import DatabaseOperations
        self.ops = DatabaseOperations(self)
        name = backend_utils.truncate_name(name.upper(), self.ops.max_name_length())
        return name.lower()

comment:10 Changed 6 years ago by Manel Clos

Resolution: fixed
Status: closednew
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