there are similar to `alter table drop column` issue: `alter table rename column`, `drop table`, `rename table`. (honestly `alter table drop column` and `drop table` a bit different wiith `alter table remane column` and `rename table`)
Look like you general flow for migration: 1. change code and create migrations 2. apply migrations 3. apply code for all your instances the issue in this cases I can describe: we have code that we still used. for `alter table drop column`, `drop table` next scenario works fine (as your temp solution too): 1. remove column/table usage from codebase 2. apply this code for all of your instances 3. apply migration with field/table removal But if you mix migrations for `alter table add column` and `alter table drop column` - you cannot safely apply both migrations simultaneously, and your proposal sounds pretty reasonable there. However if you add disabled option, then make migration, remove field, then make migration, then apply this changes to your environment - you will get same issue. So to automate deployment process and to get achievable result you want I think you need something more complex: deploying atomic changes, but for me it sounds more about deployment than django itself. On Monday, 24 June 2019 16:15:04 UTC+3, Matthieu Rudelle wrote: > > Hi there, > > I can't find any previous ticket proposing a solution to this problem so > here are my findings: > > **Use case**: > When using continuous delivery several versions of the code can be running > in parallel on se same DB. Say for instance that release 2.42 is in > production, 2.43 is about to be rolled out and in this release one field > (say ''MyModel.my_unused_field'') is not used anymore and was removed. > Before rolling out 2.43 the DB is migrated and column ''my_unused_field'' > of ''MyModel'' is removed. This makes 2.42 crash saying that one column is > not found even though 2.42 does not use the field anywhere in the code. > > **Temporary solution**: > Do not makemigrations until de 2.44 release, but it does not scale well > with many contributors and CI tools (doing their awesome job of making sure > migrations and models are in sync) will complain. > > **Proposed solution**: > Have a ''disabled'' param on Field. When activated this field is not > fetched from the DB but replaced by a hardcoded value. > In our use case, ''disabled'' is added at the 2.42 release, then when 2.43 > rolls out and migrates the DB no error is thrown. > > **Refs**: > - django-users discussion: > https://groups.google.com/forum/#!topic/django-users/HY_6rZZ0Kk8 > - the same problem discussed in this article, but with a slightly > different solution: > https://pankrat.github.io/2015/django-migrations-without-downtimes/#django-wishlist > > (third item in the wishlist) > - Previous django-developpers discussion: > https://groups.google.com/d/msg/django-developers/5ofrxeLT95E/XhppgA_KAQAJ > > What do you guys think? > -- You received this message because you are subscribed to the Google Groups "Django developers (Contributions to Django itself)" group. To unsubscribe from this group and stop receiving emails from it, send an email to django-developers+unsubscr...@googlegroups.com. To post to this group, send email to django-developers@googlegroups.com. Visit this group at https://groups.google.com/group/django-developers. To view this discussion on the web visit https://groups.google.com/d/msgid/django-developers/0422ed55-5c7f-4ed2-b096-7df02311b917%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
