119 lines
4.7 KiB
Python
119 lines
4.7 KiB
Python
import hashlib
|
|
|
|
from django.db.backends.utils import split_identifier
|
|
from django.utils.encoding import force_bytes
|
|
|
|
__all__ = ['Index']
|
|
|
|
|
|
class Index:
|
|
suffix = 'idx'
|
|
# The max length of the name of the index (restricted to 30 for
|
|
# cross-database compatibility with Oracle)
|
|
max_name_length = 30
|
|
|
|
def __init__(self, *, fields=(), name=None, db_tablespace=None):
|
|
if not isinstance(fields, (list, tuple)):
|
|
raise ValueError('Index.fields must be a list or tuple.')
|
|
if not fields:
|
|
raise ValueError('At least one field is required to define an index.')
|
|
self.fields = list(fields)
|
|
# A list of 2-tuple with the field name and ordering ('' or 'DESC').
|
|
self.fields_orders = [
|
|
(field_name[1:], 'DESC') if field_name.startswith('-') else (field_name, '')
|
|
for field_name in self.fields
|
|
]
|
|
self.name = name or ''
|
|
if self.name:
|
|
errors = self.check_name()
|
|
if len(self.name) > self.max_name_length:
|
|
errors.append('Index names cannot be longer than %s characters.' % self.max_name_length)
|
|
if errors:
|
|
raise ValueError(errors)
|
|
self.db_tablespace = db_tablespace
|
|
|
|
def check_name(self):
|
|
errors = []
|
|
# Name can't start with an underscore on Oracle; prepend D if needed.
|
|
if self.name[0] == '_':
|
|
errors.append('Index names cannot start with an underscore (_).')
|
|
self.name = 'D%s' % self.name[1:]
|
|
# Name can't start with a number on Oracle; prepend D if needed.
|
|
elif self.name[0].isdigit():
|
|
errors.append('Index names cannot start with a number (0-9).')
|
|
self.name = 'D%s' % self.name[1:]
|
|
return errors
|
|
|
|
def create_sql(self, model, schema_editor, using=''):
|
|
fields = [model._meta.get_field(field_name) for field_name, _ in self.fields_orders]
|
|
col_suffixes = [order[1] for order in self.fields_orders]
|
|
return schema_editor._create_index_sql(
|
|
model, fields, name=self.name, using=using, db_tablespace=self.db_tablespace,
|
|
col_suffixes=col_suffixes,
|
|
)
|
|
|
|
def remove_sql(self, model, schema_editor):
|
|
quote_name = schema_editor.quote_name
|
|
return schema_editor.sql_delete_index % {
|
|
'table': quote_name(model._meta.db_table),
|
|
'name': quote_name(self.name),
|
|
}
|
|
|
|
def deconstruct(self):
|
|
path = '%s.%s' % (self.__class__.__module__, self.__class__.__name__)
|
|
path = path.replace('django.db.models.indexes', 'django.db.models')
|
|
kwargs = {'fields': self.fields, 'name': self.name}
|
|
if self.db_tablespace is not None:
|
|
kwargs['db_tablespace'] = self.db_tablespace
|
|
return (path, (), kwargs)
|
|
|
|
def clone(self):
|
|
"""Create a copy of this Index."""
|
|
_, _, kwargs = self.deconstruct()
|
|
return self.__class__(**kwargs)
|
|
|
|
@staticmethod
|
|
def _hash_generator(*args):
|
|
"""
|
|
Generate a 32-bit digest of a set of arguments that can be used to
|
|
shorten identifying names.
|
|
"""
|
|
h = hashlib.md5()
|
|
for arg in args:
|
|
h.update(force_bytes(arg))
|
|
return h.hexdigest()[:6]
|
|
|
|
def set_name_with_model(self, model):
|
|
"""
|
|
Generate a unique name for the index.
|
|
|
|
The name is divided into 3 parts - table name (12 chars), field name
|
|
(8 chars) and unique hash + suffix (10 chars). Each part is made to
|
|
fit its size by truncating the excess length.
|
|
"""
|
|
_, table_name = split_identifier(model._meta.db_table)
|
|
column_names = [model._meta.get_field(field_name).column for field_name, order in self.fields_orders]
|
|
column_names_with_order = [
|
|
(('-%s' if order else '%s') % column_name)
|
|
for column_name, (field_name, order) in zip(column_names, self.fields_orders)
|
|
]
|
|
# The length of the parts of the name is based on the default max
|
|
# length of 30 characters.
|
|
hash_data = [table_name] + column_names_with_order + [self.suffix]
|
|
self.name = '%s_%s_%s' % (
|
|
table_name[:11],
|
|
column_names[0][:7],
|
|
'%s_%s' % (self._hash_generator(*hash_data), self.suffix),
|
|
)
|
|
assert len(self.name) <= self.max_name_length, (
|
|
'Index too long for multiple database support. Is self.suffix '
|
|
'longer than 3 characters?'
|
|
)
|
|
self.check_name()
|
|
|
|
def __repr__(self):
|
|
return "<%s: fields='%s'>" % (self.__class__.__name__, ', '.join(self.fields))
|
|
|
|
def __eq__(self, other):
|
|
return (self.__class__ == other.__class__) and (self.deconstruct() == other.deconstruct())
|