# Repairing migrations

**URL:** <https://www.ruby-forum.com/t/repairing-migrations/109881>\
**Category:** Rails\
**Created:** [July 19, 2007, 10:08pm UTC](https://www.ruby-forum.com/t/repairing-migrations/109881 "2007-07-19T22:08:50Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![magic\_hat](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/5daacb/32.png) [@magic\_hat](https://www.ruby-forum.com/u/magic_hat)\
**Post date:** [July 19, 2007, 10:08pm UTC](https://www.ruby-forum.com/t/repairing-migrations/109881/1 "2007-07-19T22:08:50Z")

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So occassionally my migrations go…uh… off the rails. One of them  
fails, and then I start getting errors about fields already existing,  
etc. Or I make some changes to a database by hand, and then need to  
bring the migration back in synch with the db without nuking the db  
contents.

Sometimes I can turn the schema into a migration to accomplish this.  
But other times the errors continue. Is there a better way to bring a  
migration and existing db into synch?

Thanks!

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**Author:** ![magic\_hat](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/5daacb/32.png) [@magic\_hat](https://www.ruby-forum.com/u/magic_hat)\
**Post date:** [July 19, 2007, 11:11pm UTC](https://www.ruby-forum.com/t/repairing-migrations/109881/2 "2007-07-19T23:11:02Z")

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magic\_hat wrote:

> So occassionally my migrations go…uh… off the rails. One of them  
> fails, and then I start getting errors about fields already existing,  
> etc. Or I make some changes to a database by hand, and then need to  
> bring the migration back in synch with the db without nuking the db  
> contents.
> 
> Sometimes I can turn the schema into a migration to accomplish this.  
> But other times the errors continue. Is there a better way to bring a  
> migration and existing db into synch?

The biggest thing is to test your migration in the development  
environment. That will get rid of many problems. But if for some reason  
your migration get’s an error in the production environment you can just  
comment out the part of the migration it has already done (you can tell  
by where the error occured) then run again. That migration has not be  
checked off yet it will just skip your commented section and pick up  
where it left off.

Alternatively you can make the rest of the changes manually and then  
just bump the version in the schema table to make rails think you ran  
it.

Eric

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<div class="post-metadata">

**Author:** ![magic\_hat](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/5daacb/32.png) [@magic\_hat](https://www.ruby-forum.com/u/magic_hat)\
**Post date:** [July 19, 2007, 11:19pm UTC](https://www.ruby-forum.com/t/repairing-migrations/109881/3 "2007-07-19T23:19:02Z")

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On 7/19/07, Eric A. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> > migration and existing db into synch?  
> > just bump the version in the schema table to make rails think you ran it.
> 
> Eric

Or you could use a real database that supports transactional DDL.

Pat

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<div class="post-metadata">

**Author:** ![magic\_hat](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/5daacb/32.png) [@magic\_hat](https://www.ruby-forum.com/u/magic_hat)\
**Post date:** [July 19, 2007, 11:24pm UTC](https://www.ruby-forum.com/t/repairing-migrations/109881/4 "2007-07-19T23:24:04Z")

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On 19-Jul-07, at 5:09 PM, Eric A. wrote:

> > migration and existing db into synch?  
> > where it left off.
> 
> Alternatively you can make the rest of the changes manually and then  
> just bump the version in the schema table to make rails think you  
> ran it.
> 
> Eric

I have, to date, found two bad habits cause havoc - if you don’t do  
these two you will have more migration smiles.

1. don’t edit by tables with your sql tool - always use migrations  
if you’re gonna use a system, us it - otherwise pain is your reward

2. don’t edit old migrations - you’re running the the risk of  
creating a migration that’s gonna break something.  
Keep moving forward. I’ve you’ve got a new column, then create a  
migration that ads the column - don’t edit the original create migration

If you do the above (and test your migration) you won’t have to do  
any column check tricks

cheers,  
Jodi

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<div class="post-metadata">

**Author:** ![magic\_hat](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/5daacb/32.png) [@magic\_hat](https://www.ruby-forum.com/u/magic_hat)\
**Post date:** [August 11, 2007, 12:00pm UTC](https://www.ruby-forum.com/t/repairing-migrations/109881/5 "2007-08-11T12:00:21Z")

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An improvement is ro run your migrations in a transaction.  
[http://www.redhillonrails.org](http://www.redhillonrails.org) has a grat plugin for this (Transactional  
migrations)

Regards  
Wim

Jodi S. wrote:

> > > 
> > 
> > tell
> 
> migration that ads the column - don’t edit the original create migration
> 
> If you do the above (and test your migration) you won’t have to do  
> any column check tricks
> 
> cheers,  
> Jodi
> 
> >

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