Allow AlterOrderWithRespectTo to order existing data

[Markus Holtermann]

Following #23983 it might be worth it to add a flag to AlterOrderWithRespectTo to order existing data (off by default for backwards compat and as this might cause serious performance problems on large tables). The MigrationQuestioner could then ask (and warn) for that flag.

[mhall1]

I apologize but I have to release this ticket because I'm leaving on vacation and its still waiting for approval by the core team.

[Tim Graham]

@mhall1, you probably didn't realize since you marked the ticket as "Accepted" it doesn't appear in the unreviewed ticket queue to get feedback. Anyway, the ideas seems okay to me although I am not quite sure what the implementation would look like -- would the questioner iterate through all the rows and ask for an order # or something else?

[Markus Holtermann]

I suggest to order the existing rows by the default ordering of the related model (the owrt is defined on).

[mhall1]

Oh okay, thanks for the tip @timgraham.