Re: ERXMigrationDatabase and postUpgrade
Re: ERXMigrationDatabase and postUpgrade
- Subject: Re: ERXMigrationDatabase and postUpgrade
- From: Sanford Selznick <email@hidden>
- Date: Sat, 11 Apr 2009 08:57:57 -0700
At 7:50 AM -0700 4/11/09, Mike Schrag wrote:
one is that your model will change over time and the constant you
refer to in migration0 might not exist in a month, so it would
stop compiling.
I _want_ the compiler error. I'd much rather get a compiler error
than a runtime error.
No you don't :)
Well, not for this at least ... the point of migrations is that
things change. if you ever delete a column from your database you
would break HISTORICAL state. this is the same reason why you can't
touch anything related to an EOModel inside your migration method,
because your EOModel and java files always only ever match LATEST
state, but you have to be able to migrate from old state that no
longer matches the latest models and java files. If you remove a
column in version 3, you would break your version 1 where it
existed, which is incorrect -- you would be changing history. You
have to be able to play back db changes exactly as they were
regardless of the current state of your models.
An excellent point. And since migration code is machine generated,
chance for error is reduced too. This is definitely an exception to
my "string constants are bad" rule. :-)
Best,
Sanford
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