Re: [gentoo-user] [OT] Looking for a tool to produce 'reverse' SQL

[kashani <kashani-list@badapple.net>]

Benjamin Blazke wrote:
> 
> --- kashani <kashani-list@badapple.net> wrote:
> 
>> The tool you're looking for is called a DBA. :-)
> 
> I see. So it's up to QA to test extensively and up to
> the DBA to recover from a disaster.
> 
> I hoped there would be a more automated solution but
> it seems that it's not really doable. Thanks for such
> a quick answer ;-) 

	That's pretty much the way we've been doing it, but if there is a 
better way I'd like to hear it too as I'm a poor imitation of a DBA. 
However I don't see any easy solutions for combined application, data, 
schema change rollbacks especially when changes to one cause 
dependencies in others.

	As an illustration you change u_user.login_name to varchar(64) from 
varchar(32). Users start creating longer users names. A few hours later 
you find some problems in how your application handles longer names. If 
you needed to rollback the alter table command is easy, but some of your 
data would now be invalid. Rather than rollback the easier fix is to 
update the application and hopefully the change is a single file update.

	I still think there are cases when you could rollback, but they'd have 
to be so simple that having a tool to generate the sql would be overkill.

Ramin
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