从Windows命令行运行脚本时，由于“ SQL语句正在进行”，Python sqlite3无法回滚事务。

Question

I'm operating table merges on some sqlite3 databases in Python. When one of the merging functions spots an error due to a condition, it returns False. If a False is returned then a rollback is performed. Something like this:

con_out = sqlite3.connect('db',isolation_level=None)
out_cursor = con_out.cursor()
try:
   out_cursor.execute("begin")
   if not merge_table(in_cursor, out_cursor, verbose):
      logging.error("rolling back changes")
      out_cursor.execute("rollback")
      return False
except Exception as e:
   logging.error("rolling back changes: %s" % (str(e)))
   out_cursor.execute("rollback")
   return False

Now when this code is executed from PyCharm interpreter, and a False is returned, there is no problem. It rolls back normally as expected. However, when the script is run from Windows command line, it gives me this error:

sqlite3.OperationalError: cannot rollback transaction - SQL statements in progress

Answer 1

Just in case if anyone wondering, I found the problem. Before I even set the isolation_level of the database to None, I execute:

out_cursor.execute("PRAGMA journal_mode = MEMORY")
db_con_out.commit()

For some reason this statement was not committing and was still in progress, blocking other transactions. When I wrapped it with this code down below, it worked

db_con_out.isolation_level = None
db_cursor.execute("begin")
if not execute_sql(db_cursor, "PRAGMA journal_mode = MEMORY;"):
    db_cursor.execute("rollback")
    sys.exit()
else:
    db_cursor.execute("commit")

It commit just fine telling from the debugger. I don't know the actual reason behind this though.