Hi!
The database migration system in Django 1.7 is really great and
seems to work very well. However, since I'm a long-time South
user, there's one feature that I'm missing: the possibility to
update an existing migration (the --update flag to South's
schemamigration command).
I think it's an important feature because it allows you to make
massive changes to your models when developing a new feature, because
it rolls back the migration and rewrites it, effectively wiping
everything and starting from scratch for that migration. I can rename
tables, change foreign keys to normal fields and vice versa,
add/remove/rename M2M fields freely, etc., things that the migrations
don't normally handle very well automatically. When developing,
there's no need to retain data, so it's OK to roll back and lose all
the data in newly created tables, for example. It's also not very
efficient to leave all those intermediate steps in the migration
history to wait until squashmigrations is used some time in the
future.
As a proof-of-concept, I created a shell script that does the
migration updating for a given app. It's not an universal
solution because it's tied to a certain directory hierarchy,
though. Here it is:
#!/bin/sh
project=PROJECTNAME
app=$1
cur=$(./manage.py migrate --list $app | tail -n 1 | grep '\[X\]' | sed 's/
\[X\] //')
prev=$(./manage.py migrate --list $app | tail -n 2 | head -n 1 | grep '\[X\]' |
sed 's/ \[X\] //')
if [ -z "$cur" -o -z "$prev" ]; then
echo "Unable to find out current or previous migration. Have you run all
migrations?"
exit 1
fi
echo "Rolling back to:" $prev
echo "Deleting and updating:" $cur
echo "Are you sure? [yN]"
read x
[ "$x" != "y" ] && exit 0
./manage.py migrate "$app" "$prev"
rm $project/$app/migrations/$cur.py
./manage.py makemigrations "$app"
What do you think? Could functionality like this be added to Django?
Are there problems I've missed with this approach?
Petri
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