def add_select_related(self, fields):
"""
If in fields is related_field for translations, will be replaced by fields in proper languages.
"""
new_fields = []
extra_select = {}
opts = self.model._meta
trans_opts = opts.translation_model._meta
# TODO: fix this
#related_name = trans_opts.related_name
related_name = 'translations'
translation_fields = [f.name for f in trans_opts.fields if f.name not in ('master', 'language_code')]
for field in fields:
# usual select_related
if not field.startswith(related_name):
new_fields.append(field)
continue
# get language
if field == related_name:
language_code = get_active()
else:
field_and_lang = field.rsplit('_', 1)
# Coincidental field name might occur if language_code is not correct, do not do anything as
# select_related does not raise errors if used with incorrect fields
if len(field_and_lang) != 2 or field_and_lang[1] not in get_all():
new_fields.append(field)
continue
field, language_code = field_and_lang
# This is main code of this method, build extra_select that might be used by fill_translation_cache
for trans_field in translation_fields:
extra_select[get_field_alias(trans_field, language_code)] = '%s.%s' % (
get_table_alias(trans_opts.db_table, language_code),
connection.ops.quote_name(trans_field)
)
# XXX: this is not safe if translation model has no fields, can it happen??
# join translatable model (original) table if not joined yet
alias = self.get_initial_alias()
# join translation table if not joined yet
translation_fields.remove(trans_opts.pk.name)
self.setup_joins(
['%s_%s' % (translation_fields[0], language_code)], # any translated_field
opts,
alias,
True,
can_reuse = set([alias])
)
if extra_select:
self.add_extra(extra_select, None, None, None, None, None)
super(MultilingualQuery, self).add_select_related(new_fields)
def setup_joins(self, names, opts, alias, dupe_multis, allow_many=True,
allow_explicit_fk=False, can_reuse=None, negate=False,
process_extras=True):
"""
This overrides setup_joins method in case we want to join multilingual field.
This is hell good place to rewrite something because it is called for every time when we care.
"""
# So far we only handle fields that are local for TranslationModel (not related)
# so we can only take care of first of names, see NotImplementedError lower
field_name = names[0]
field = getattr(self.model, field_name, None)
# Field is not multilingual, proceed as usual
if not field or not isinstance(field, TranslationProxyField):
return super(MultilingualQuery, self).setup_joins(
names, opts, alias, dupe_multis, allow_many, allow_explicit_fk, can_reuse, negate, process_extras
)
if len(names) > 1:
raise NotImplementedError('MultilingualQuery can not now handle relations through multilingual fields')
# This resolves defaults as well
language_code = field.language_code
translation_cls = opts.translation_model
translation_opts = translation_cls._meta
target_field = translation_opts.get_field(field._field_name)
trans_table_name = translation_opts.db_table
table_alias = get_table_alias(trans_table_name, language_code)
# Exclude table aliases for other languages to prevent language mismatch
# TEST: filter(name_en="some", name_cs="neco")
exclusions = set(self.table_map.get(trans_table_name, [])) - set([table_alias])
# Enable reusing of translation table alias for required language so translations for one language are
# added only once
# TEST: filter(name_en="some").values('name_en')
reuse = can_reuse or set()
reuse.add(table_alias)
# Important step 1: join translation table under language-specific alias
# QUESTION: is LEFT OUTER JOIN always required?
# HACK: this is hell of a hack, but it is only way that django enables for extra joins now :-(
# Still hopes, that it will get better someday and there will be correct way how add condition into join
# XXX: did not work in MySQL, so take quoting from default database until correctly fixed
qn = connection.ops.quote_name
right_column = '%s AND \'%s\' = %s.%s' % (
qn('master_id'),
language_code,
table_alias, # do not quote, it is alias
qn('language_code')
)
trans_alias = self.join((alias, trans_table_name, opts.pk.column, right_column), always_create=True,
reuse=reuse, exclusions=exclusions, promote=True, nullable=True)
# Important step 2: if required alias has not been defined yet, new alias is created in during join
# We change the alias to language-specific alias, so we can check whether it is already present
if trans_alias != table_alias:
self.change_aliases({trans_alias: table_alias})
# Return target field on target model, target field in database, target model options
# and some other fields I do not know what they are for :-)
return target_field, target_field, translation_opts, [table_alias], [0, 1], []
