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from __future__ import print_function
import uuid
from django.db.backends.util import truncate_name
from south.db import generic
class DatabaseOperations(generic.DatabaseOperations):
"""
PsycoPG2 implementation of database operations.
"""
backend_name = "postgres"
def create_index_name(self, table_name, column_names, suffix=""):
"""
Generate a unique name for the index
Django's logic for naming field indexes is different in the
postgresql_psycopg2 backend, so we follow that for single-column
indexes.
"""
if len(column_names) == 1:
return truncate_name(
'%s_%s%s' % (table_name, column_names[0], suffix),
self._get_connection().ops.max_name_length()
)
return super(DatabaseOperations, self).create_index_name(table_name, column_names, suffix)
@generic.copy_column_constraints
@generic.delete_column_constraints
def rename_column(self, table_name, old, new):
if old == new:
# Short-circuit out
return []
self.execute('ALTER TABLE %s RENAME COLUMN %s TO %s;' % (
self.quote_name(table_name),
self.quote_name(old),
self.quote_name(new),
))
@generic.invalidate_table_constraints
def rename_table(self, old_table_name, table_name):
"will rename the table and an associated ID sequence and primary key index"
# First, rename the table
generic.DatabaseOperations.rename_table(self, old_table_name, table_name)
# Then, try renaming the ID sequence
# (if you're using other AutoFields... your problem, unfortunately)
if self.execute(
"""
SELECT 1
FROM information_schema.sequences
WHERE sequence_name = %s
""",
[old_table_name + '_id_seq']
):
generic.DatabaseOperations.rename_table(self, old_table_name + "_id_seq", table_name + "_id_seq")
# Rename primary key index, will not rename other indices on
# the table that are used by django (e.g. foreign keys). Until
# figure out how, you need to do this yourself.
pkey_index_names = self.execute(
"""
SELECT pg_index.indexrelid::regclass
FROM pg_index, pg_attribute
WHERE
indrelid = %s::regclass AND
pg_attribute.attrelid = indrelid AND
pg_attribute.attnum = any(pg_index.indkey)
AND indisprimary
""",
[table_name]
)
if old_table_name + "_pkey" in pkey_index_names:
generic.DatabaseOperations.rename_table(self, old_table_name + "_pkey", table_name + "_pkey")
def rename_index(self, old_index_name, index_name):
"Rename an index individually"
generic.DatabaseOperations.rename_table(self, old_index_name, index_name)
def _default_value_workaround(self, value):
"Support for UUIDs on psql"
if isinstance(value, uuid.UUID):
return str(value)
else:
return super(DatabaseOperations, self)._default_value_workaround(value)
def _db_type_for_alter_column(self, field):
return self._db_positive_type_for_alter_column(DatabaseOperations, field)
def _alter_add_column_mods(self, field, name, params, sqls):
return self._alter_add_positive_check(DatabaseOperations, field, name, params, sqls)
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