Waiting for DB restore to finish using sqlalchemy on SQL Server 2008

问题

I'm trying to automate my db restores during development, using TSQL on SQL Server 2008, using sqlalchemy with pyodbc as a transport.

The command I'm executing is:

"""CREATE DATABASE dbname

restore database dbname FROM DISK='C:\Backups\dbname.bak' WITH REPLACE,MOVE 'dbname_data' TO 'C:\Databases\dbname_data.mdf',MOVE 'dbname_log' TO 'C:\Databases\dbname_log.ldf'"""

Unfortunately, the in SQL Management Studio, after the code has run, I see that the DB remains in state "Restoring...".

If I restore through management studio, it works. If I use subprocess to call "sqlcmd", it works. pymssql has problems with authentication and doesnt even get that far.

What might be going wrong?

回答1:

The BACKUP and RESTORE statements run asynchronously so they don't terminate before moving on to the rest of the code.

Using a while statement as described at http://ryepup.unwashedmeme.com/blog/2010/08/26/making-sql-server-backups-using-python-and-pyodbc/ solved this for me:

# setup your DB connection, cursor, etc
cur.execute('BACKUP DATABASE ? TO DISK=?', 
            ['test', r'd:\temp\test.bak'])
while cur.nextset():
    pass

回答2:

Unable to reproduce the problem restoring directly from pyodbc (without sqlalchemy) doing the following:

connection = pyodbc.connect(connection_string) # ensure autocommit is set to `True` in connection string
cursor = connection.cursor()
affected = cursor.execute("""CREATE DATABASE test
RESTORE DATABASE test FROM DISK = 'D:\\test.bak' WITH REPLACE, MOVE 'test_data' TO 'D:\\test_data.mdf', MOVE 'test_log' to 'D:\\test_log.ldf' """)
while cursor.nextset():
    pass

Some questions that need clarification:

What is the code in use to do the restore using sqlalchemy?
What version of the SQL Server ODBC driver is in use?
Are there any messages in the SQL Server log related to the restore?

Thanks to geographika for the Cursor.nextset() example!

回答3:

Five things fixed my problem with identical symptoms.

Found that my test.bak file contained the wrong mdf and ldf files:

>>> cursor.execute(r"RESTORE FILELISTONLY FROM DISK = 'test.bak'").fetchall()    
[(u'WRONGNAME', u'C:\\Program Files\\Microsoft SQL ...),
(u'WRONGNAME_log', u'C:\\Program Files\\Microsoft SQL ...)]

Created a new bak file and made sure to set the copy-only backup option

Set the autocommit option for my connection.

connection = pyodbc.connect(connection_string, autocommit=True)

Used the connection.cursor only for a single RESTORE command and nothing else

Corrected the test_data MOVE to test in my RESTORE command (courtesy of @beargle).

affected = cursor.execute("""RESTORE DATABASE test FROM DISK = 'test.bak' WITH REPLACE, MOVE 'test' TO 'C:\\test.mdf', MOVE 'test_log' to 'C:\\test_log.ldf' """)

回答4:

For SQL Alchemy users, and thanks to geographika for the answer: I ended up using the “raw” DBAPI connection from the connection pool.

It is exactly as geographika's solution but with a few additional pieces:

import sqlalchemy as sa
driver = 'SQL+Server'
name = 'servername'
sql_engine_str = 'mssql+pyodbc://'\
                     + name\
                     + '/'\
                     + 'master'\
                     + '?driver='\
                     + driver
engine = sa.create_engine(sql_engine_str, connect_args={'autocommit': True})

connection = engine.raw_connection()
try:
  cursor = connection.cursor()
  sql_cmd = """
        RESTORE DATABASE [test]
        FROM DISK = N'...\\test.bak'
        WITH FILE = 1,
         MOVE N'test'
         TO N'...\\test_Primary.mdf',
         MOVE N'test_log'
         TO N'...\\test_log.ldf',
         RECOVERY,
         NOUNLOAD,
         STATS = 5,
         REPLACE
        """
  cursor.execute(sql_cmd)
  while cursor.nextset():
       pass
except Exception as e:
  logger.error(str(e), exc_info=True)

来源：https://stackoverflow.com/questions/4254581/waiting-for-db-restore-to-finish-using-sqlalchemy-on-sql-server-2008

标签

sql-server

tsql

sqlalchemy

restore

pyodbc