On 15/03/2017 7:12 PM, Stefano Tranquillini wrote:
Hi people.
I've to do a migration for the database, specifically I've to rename a
table.
To do so I've a RunPython that runs this sql statemnet
`ALTER TABLE "old_table" RENAME TO "new_table"`
First question: should I use
https://docs.djangoproject.com/en/1.8/ref/migration-operations/#renamemodel
, does it do the same?
I believe it does the same ... certainly worked for me with Postgres.
Make an empty migration.
operations = [
migrations.RenameModel('Oldname', 'Newname'),
migrations.AlterModelTable('Newname', 'appname_newname'),
]
Will these operation update all the refrences in the code, such that
django will keep working without problems?
Definitely not.
The process I used was ...
1. Change the model name in your code
2. Run the dev server and fix everything which barfs. I think unit
testing creates its test database from your models rather than by
copying the database so unit tests should be fixable with
search/replace. However, any fixtures involved will undoubtedly spoil
things. ymmv.
3. Migrate and resolve any remaining issues.
Rollout to the two servers sounds like a transation nightmare to me. I
think I'd say some things are possible but expensive because you have to
set up duplicated systems for practicing such rollouts or you down the
system for a short time to make sure the data is protected.
ALSO
I have had migration squashing issues (circular references) since then.
It may or may not be the reason but I think in hindsight I would squash
all migrations prior to renaming the table.
Good luck
Mike
Now, I'm using postgres and I've two servers using the same DB, let's
call them A and B. when I'll rename the table the code will break, so
the procedure will be:
- stop A
- update A
- migrate
- stop B
- start A
The problem is, that I've to be sure that migrations are atomic and
have a transaction that locks the DB (or that table). Reading the
documentation I found:
/On databases that do support DDL transactions (SQLite and
PostgreSQL), |RunPython| operations do not have any transactions
automatically added besides the transactions created for each
migration./ -
https://docs.djangoproject.com/en/1.10/ref/migration-operations/ (I'm
using 1.8)
If i go with renameModel, will it be in a single transaction?
What I want to avoid is to stop both A and B to perform migrations.
It would be better to do the migration and then stop B, this should
have a down that is smaller compared to stopping all services and the
run them again.
any suggestion?
Ciao
--
You received this message because you are subscribed to the Google
Groups "Django users" group.
To unsubscribe from this group and stop receiving emails from it, send
an email to [email protected]
<mailto:[email protected]>.
To post to this group, send email to [email protected]
<mailto:[email protected]>.
Visit this group at https://groups.google.com/group/django-users.
To view this discussion on the web visit
https://groups.google.com/d/msgid/django-users/3205d24d-537b-4819-b2e4-e1adc31a3d46%40googlegroups.com
<https://groups.google.com/d/msgid/django-users/3205d24d-537b-4819-b2e4-e1adc31a3d46%40googlegroups.com?utm_medium=email&utm_source=footer>.
For more options, visit https://groups.google.com/d/optout.
--
You received this message because you are subscribed to the Google Groups "Django
users" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
To post to this group, send email to [email protected].
Visit this group at https://groups.google.com/group/django-users.
To view this discussion on the web visit
https://groups.google.com/d/msgid/django-users/9495b772-78d1-95ad-1063-4742326cb235%40dewhirst.com.au.
For more options, visit https://groups.google.com/d/optout.
