问题
I have about 1000 user account entities like this:
class UserAccount(ndb.Model):
email = ndb.StringProperty()
Some of these email values contain uppercase letters like JohnathanDough@email.com. I want to select all the email values from all UserAccount entities and apply python's email.lower(). How can I do this efficiently, and most importantly, without errors?
Note: The email values are important for login, so I cannot afford to mess this up. Is there a way to backup this data in case of the event that I do make a mistake?
Thank you.
回答1:
Yes, off course. Even if Datastore Administration is an experimental feature we can backup and restore data without coding. Follow this instruction for the backup flow: Backing up data. To processing your data instead, the most efficient way is to use the MapReduce library.
回答2:
Mapreduce works but its an excesive complication if youve never done it before.
Use task queues, each can handle a query result page, store the next pageToken and start another taskqueue for the next page.
Slower than mapreduce if you run the taskqueues secuentially. 1000 entries ia not much. Maybe in one minute it will be done.
来源：https://stackoverflow.com/questions/24455850/google-app-engine-modifying-1000-entities