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import logging
import sqlalchemy
from camelot.core.utils import ugettext as _
from camelot.core.conf import settings
logger = logging.getLogger('camelot.core.backup')
[docs]class BackupMechanism(object):
"""Create a backup of the current database to an sqlite database stored in
a file.
The backupmechanism always considers the schema of the backed up database
as the master, and never that of the backup. This means that when a backup
is made, the backup file is first removed, and then filled with the tables
from the the database to backup. When a restore is done, the schema of the
database is not touched, but the tables are emptied and the data from the
backup is copied into the existing schema.
"""
def __init__(self, filename, storage=None):
"""Backup and restore to a file using it as an sqlite database.
:param filename: the name of the file in which to store the backup, this
can be either a local file or the name of a file in the storage.
:param storage: a storage in which to store the file, if None is given,
it is assumed that the file should be stored or retrieved from the local
filesystem.
"""
self._filename = unicode(filename)
self._storage = storage
@classmethod
[docs] def get_filename_prefix(cls):
"""
:return: a string with the prefix for the default name of the backup file
By default this method returns an empty string, overwrite this method to
return a custom string, like the name of the company or such.
This method will be called inside the model thread.
"""
return u''
@classmethod
[docs] def get_default_storage(cls):
"""
:return: a camelot.core.files.storage.Storage object
Returns the storage to be used to store default backups.
By default, this will return a Storage that puts the backup files
in the DataLocation as specified by the QDesktopServices
"""
from PyQt4.QtGui import QDesktopServices
apps_folder = unicode(QDesktopServices.storageLocation(QDesktopServices.DataLocation))
from camelot.core.files.storage import Storage
return Storage(upload_to='backups', root=apps_folder)
[docs] def backup_table_filter(self, from_table):
"""
Method used to filter which tables should be backed up, overwrite this method
for taking into account specific schema issues.
:from_table: the table that is considered for backup
:return: True when the table should be backed up
"""
return True
[docs] def restore_table_filter(self, from_table):
"""
Method used to filter which tables should be restored, overwrite this method
for taking into account specific schema issues. restore_table_filter is different
from backup_table_filter, since we might want to store data in the backup that
should not be restored, like schema version information.
:from_table: the table that is considered for backup
:return: True when the table should be restored
"""
return True
[docs] def prepare_schema_for_restore(self, from_engine, to_engine):
"""This method will be called before the actual restore starts. It allows bringing
the schema at the same revision as the backed up data.
"""
pass
[docs] def update_schema_after_restore(self, from_engine, to_engine):
"""This method will be called after the restore has been done. It allows bringing
the schema at the revision the application expects.
"""
pass
[docs] def backup(self):
"""Generator function that yields tuples :
(numer_of_steps_completed, total_number_of_steps, description_of_current_step)
while performing a backup.
"""
import os
import tempfile
import shutil
from sqlalchemy import create_engine
from sqlalchemy import MetaData, Table, Column
from sqlalchemy.pool import NullPool
from sqlalchemy.dialects import mysql as mysql_dialect
from sqlalchemy.dialects import postgresql as postgresql_dialect
import sqlalchemy.types
yield (0, 0, _('Analyzing database structure'))
from_engine = settings.ENGINE()
from_meta_data = MetaData()
from_meta_data.bind = from_engine
from_meta_data.reflect()
yield (0, 0, _('Preparing backup file'))
#
# We'll first store the backup in a temporary file, since
# the selected file might be on a server or in a storage
#
file_descriptor, temp_file_name = tempfile.mkstemp(suffix='.db')
os.close(file_descriptor)
logger.info("preparing backup to '%s'"%temp_file_name)
if os.path.exists(self._filename):
os.remove(self._filename)
to_engine = create_engine( u'sqlite:///%s'%temp_file_name, poolclass=NullPool )
to_meta_data = MetaData()
to_meta_data.bind = to_engine
#
# Only copy tables, to prevent issues with indices and constraints
#
from_and_to_tables = []
for from_table in from_meta_data.sorted_tables:
if self.backup_table_filter(from_table):
#print "backing up table:", from_table
#to_table = from_table.tometadata(to_meta_data)
new_cols = []
for col in from_table.columns:
new_cols.append(Column(col.name, col.type))
to_table = Table(from_table.name, to_meta_data, *new_cols)
#
# Dirty hack : loop over all columns to detect mysql TINYINT
# columns and convert them to BOOL
#
for col in to_table.columns:
if isinstance(col.type, mysql_dialect.TINYINT):
col.type = sqlalchemy.types.Boolean()
if isinstance(col.type, postgresql_dialect.DOUBLE_PRECISION):
col.type = sqlalchemy.types.Float()
if isinstance(col.type, postgresql_dialect.BYTEA):
col.type = sqlalchemy.types.LargeBinary()
#
# End of dirty hack
#
to_table.create(to_engine)
from_and_to_tables.append((from_table, to_table))
number_of_tables = len(from_and_to_tables)
for i,(from_table, to_table) in enumerate(from_and_to_tables):
yield (i, number_of_tables + 1, _('Copy data of table %s')%from_table.name)
self.copy_table_data(from_table, to_table)
yield (number_of_tables, number_of_tables + 1, _('Store backup at requested location') )
from_engine.dispose()
to_engine.dispose()
if not self._storage:
logger.info(u'move backup file to its final location')
shutil.move(temp_file_name, self._filename)
else:
logger.info(u'check backfup file in to storage with name %s'%self._filename)
self._storage.checkin( temp_file_name, self._filename )
os.remove( temp_file_name )
yield (number_of_tables + 1, number_of_tables + 1, _('Backup completed'))
[docs] def restore(self):
"""Generator function that yields tuples :
(numer_of_steps_completed, total_number_of_steps, description_of_current_step)
while performing a restore.
"""
#
# The restored database may contain different AuthenticationMechanisms
#
from camelot.model.authentication import clear_current_authentication
clear_current_authentication()
#
# Proceed with the restore
#
import os
from camelot.core.files.storage import StoredFile
from sqlalchemy import create_engine
from sqlalchemy import MetaData
from sqlalchemy.pool import NullPool
yield (0, 0, _('Open backup file'))
if self._storage:
if not self._storage.exists(self._filename):
raise Exception('Backup file does not exist')
stored_file = StoredFile(self._storage, self._filename)
filename = self._storage.checkout( stored_file )
else:
if not os.path.exists(self._filename):
raise Exception('Backup file does not exist')
filename = self._filename
from_engine = create_engine('sqlite:///%s'%filename, poolclass=NullPool )
yield (0, 0, _('Prepare database for restore'))
to_engine = settings.ENGINE()
self.prepare_schema_for_restore(from_engine, to_engine)
yield (0, 0, _('Analyzing backup structure'))
from_meta_data = MetaData()
from_meta_data.bind = from_engine
from_meta_data.reflect()
yield (0, 0, _('Analyzing database structure'))
to_meta_data = MetaData()
to_meta_data.bind = to_engine
to_meta_data.reflect()
to_tables = list(table for table in to_meta_data.sorted_tables if self.restore_table_filter(table))
number_of_tables = len(to_tables)
steps = number_of_tables * 2 + 2
for i,to_table in enumerate(reversed(to_tables)):
yield (i, steps, _('Delete data from table %s')%to_table.name)
self.delete_table_data(to_table)
for i,to_table in enumerate(to_tables):
if to_table.name in from_meta_data.tables:
yield (number_of_tables+i, steps, _('Copy data from table %s')%to_table.name)
self.copy_table_data(from_meta_data.tables[to_table.name], to_table)
yield (number_of_tables * 2 + 1, steps, _('Update schema after restore'))
self.update_schema_after_restore(from_engine, to_engine)
from_engine.dispose()
to_engine.dispose()
yield (number_of_tables * 2 + 2, steps, _('Load new data'))
from sqlalchemy.orm.session import _sessions
for session in _sessions.values():
session.expunge_all()
yield (1, 1, _('Restore completed'))
[docs] def delete_table_data(self, to_table):
"""This method might be subclassed to turn off/on foreign key checks"""
to_connection = to_table.bind.connect()
to_connection.execute(to_table.delete())
to_connection.close()
[docs] def copy_table_data(self, from_table, to_table):
from_connection = from_table.bind.connect()
query = sqlalchemy.select([from_table])
table_data = [row for row in from_connection.execute(query).fetchall()]
from_connection.close()
if len(table_data):
to_connection = to_table.bind.connect()
to_connection.execute(to_table.insert(), table_data)
if 'id' in [c.name for c in to_table.columns]:
if to_table.bind.url.get_dialect().name == 'postgresql':
table_name = to_table.name
seq_name = table_name + "_id_seq"
to_connection.execute("select setval('%s', max(id)) from %s" % (seq_name, table_name))
to_connection.close()