Fixed #13711 -- Model check added to ensure that auto-generated column name is... (91f1b6dc) · Commits · Dom Sekotill / django

django/db/backends/init.py

+0 −3

Original line number	Diff line number	Diff line
		@@ -520,9 +520,6 @@ class BaseDatabaseFeatures(object):
		# at the end of each save operation?
		supports_forward_references = True

		# Does the backend allow very long model names without error?
		supports_long_model_names = True

		# Is there a REAL datatype in addition to floats/doubles?
		has_real_datatype = False
		supports_subqueries_in_group_by = True

django/db/backends/mysql/base.py

+0 −1

Original line number	Diff line number	Diff line
		@@ -171,7 +171,6 @@ class DatabaseFeatures(BaseDatabaseFeatures):
		has_select_for_update = True
		has_select_for_update_nowait = False
		supports_forward_references = False
		supports_long_model_names = False
		# XXX MySQL DB-API drivers currently fail on binary data on Python 3.
		supports_binary_field = six.PY2
		supports_microsecond_precision = False

django/db/models/base.py

+72 −1

Original line number	Diff line number	Diff line
		@@ -12,7 +12,7 @@ from django.conf import settings
		from django.core import checks
		from django.core.exceptions import (ObjectDoesNotExist,
		MultipleObjectsReturned, FieldError, ValidationError, NON_FIELD_ERRORS)
		from django.db import (router, transaction, DatabaseError,
		from django.db import (router, connections, transaction, DatabaseError,
		DEFAULT_DB_ALIAS, DJANGO_VERSION_PICKLE_KEY)
		from django.db.models.deletion import Collector
		from django.db.models.fields import AutoField, FieldDoesNotExist
		@@ -1068,6 +1068,7 @@ class Model(six.with_metaclass(ModelBase)):
		if not cls._meta.swapped:
		errors.extend(cls._check_fields(**kwargs))
		errors.extend(cls._check_m2m_through_same_relationship())
		errors.extend(cls._check_long_column_names())
		clash_errors = cls._check_id_field() + cls._check_field_name_clashes()
		errors.extend(clash_errors)
		# If there are field name clashes, hide consequent column name
		@@ -1451,6 +1452,76 @@ class Model(six.with_metaclass(ModelBase)):
		)
		return errors

		@classmethod
		def _check_long_column_names(cls):
		"""
		Check that any auto-generated column names are shorter than the limits
		for each database in which the model will be created.
		"""
		errors = []
		allowed_len = None
		db_alias = None

		# Find the minimum max allowed length among all specified db_aliases.
		for db in settings.DATABASES.keys():
		# skip databases where the model won't be created
		if not router.allow_migrate(db, cls):
		continue
		connection = connections[db]
		max_name_length = connection.ops.max_name_length()
		if max_name_length is None:
		continue
		else:
		if allowed_len is None:
		allowed_len = max_name_length
		db_alias = db
		elif max_name_length < allowed_len:
		allowed_len = max_name_length
		db_alias = db

		if allowed_len is None:
		return errors

		for f in cls._meta.local_fields:
		_, column_name = f.get_attname_column()

		# Check if auto-generated name for the field is too long
		# for the database.
		if (f.db_column is None and column_name is not None
		and len(column_name) > allowed_len):
		errors.append(
		checks.Error(
		'Autogenerated column name too long for field "%s". '
		'Maximum length is "%s" for database "%s".'
		% (column_name, allowed_len, db_alias),
		hint="Set the column name manually using 'db_column'.",
		obj=cls,
		id='models.E018',
		)
		)

		for f in cls._meta.local_many_to_many:
		# Check if auto-generated name for the M2M field is too long
		# for the database.
		for m2m in f.rel.through._meta.local_fields:
		_, rel_name = m2m.get_attname_column()
		if (m2m.db_column is None and rel_name is not None
		and len(rel_name) > allowed_len):
		errors.append(
		checks.Error(
		'Autogenerated column name too long for M2M field '
		'"%s". Maximum length is "%s" for database "%s".'
		% (rel_name, allowed_len, db_alias),
		hint=("Use 'through' to create a separate model "
		"for M2M and then set column_name using "
		"'db_column'."),
		obj=cls,
		id='models.E019',
		)
		)

		return errors


		############################################
		# HELPER FUNCTIONS (CURRIED MODEL METHODS) #

docs/ref/checks.txt

+5 −0

Original line number	Diff line number	Diff line
		@@ -58,6 +58,11 @@ Models
		* models.E016: ``index_together/unique_together`` refers to field
		``<field_name>`` which is not local to model ``<model>``.
		* models.E017: Proxy model ``<model>`` contains model fields.
		* models.E018: Autogenerated column name too long for field ``<field>``.
		Maximum length is ``<maximum length>`` for database ``<alias>``.
		* models.E019: Autogenerated column name too long for M2M field
		``<M2M field>``. Maximum length is ``<maximum length>`` for database
		``<alias>``.

		Fields
		~~~~~~

docs/releases/1.8.txt

+22 −0

Original line number	Diff line number	Diff line
		@@ -305,6 +305,28 @@ Now to implement the same behavior, you have to create an
		``parser.add_argument`` to add any custom arguments, as parser is now an
		:py:class:`argparse.ArgumentParser` instance.

		Model check ensures auto-generated column names are within limits specified by database
		~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

		A field name that's longer than the column name length supported by a database
		can create problems. For example, with MySQL you'll get an exception trying to
		create the column, and with PostgreSQL the column name is truncated by the
		database (you may see a warning in the PostgreSQL logs).

		A model check has been introduced to better alert users to this scenario before
		the actual creation of database tables.

		If you have an existing model where this check seems to be a false positive,
		for example on PostgreSQL where the name was already being truncated, simply
		use :attr:`~django.db.models.Field.db_column` to specify the name that's being
		used.

		The check also applies to the columns generated in an implicit
		``ManyToManyField.through`` model. If you run into an issue there, use
		:attr:`~django.db.models.ManyToManyField.through` to create an explicit model
		and then specify :attr:`~django.db.models.Field.db_column` on its column(s)
		as needed.

		Miscellaneous
		~~~~~~~~~~~~~