Migration strategies for table dumps?


I’m curious how folks handle situations where you want to backup
existing data in a table before performing migrations. Say, for
example, you have a column type change, and you want to preserve the
current data and later releoad that data in case something goes wrong.

Do folks manually do a Model.find(:all) and dump it to a file in, say,
yaml format in the self.up method before any schema changes occur and
then reload it in the self.down method? Perhaps as a pseudo-fixture?
Or do people use temporary tables?

What’s the preferred strategy? And are there any builtin helpers for
this? Or is it ‘roll your own’?



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