Have you considered what would happen if a migration has a RunPython or RunSQL? They may require a certain model state.
On Tuesday, February 18, 2020 at 12:08:03 PM UTC-5, caio wrote: > > I’m working on this as a standalone PoC app for now, I may be able to > share a repository with the code soon in order to get some feedback > > Here’s in simple words where I’m at: > > * I’ve replaced the restriction of only-one-leaf-node-per-app from the > Migration Loader [1] to only-one-leaf-node-per-app-per-model. It means that > with this, you can have more than one person changing different models in > the same app, without introducing conflicts. Migrations referring to the > same app and model would still cause a conflict > > * I’m now trying to get the migration graph’s forwards/backwards plan to > handle cases where there are more than one leaf node in the graph. > > I may be doing the wrong assumption here, but it seems to me that > migrations changing different models shouldn’t introduce a real conflict? > If I have the following migration graph: > > [ 0001_initial ] => [ 0002_auto ] => [ 0003_abc ] => [ 0003_def ] => [ > 0004_auto ] > > Where 0003_abc and 0003_def don’t have any model changes in common: no FK > references, nothing related at all > > If this assumption is correct, I could have the two migrations in ANY > order in the graph, that it would still give me the same result, for > example: > > [ 0001_initial ] => [ 0002_auto ] => [ 0003_def ] => [ 0003_abc ] => [ > 0004_auto ] > > > Please let me know if I’m missing something, ideas and thoughts are really > welcome :) > > > [1] > https://github.com/django/django/blob/2a038521c4eabdc5f6d5026d3dd6d22868e329cd/django/db/migrations/loader.py#L301-L313 > > -- > Caio Ariede > caio....@gmail.com <javascript:> > > > > > On Feb 13, 2020, at 11:49, Dave Vernon <da...@springbourne-tech.com > <javascript:>> wrote: > > If I had to guess, it would be that with more than one leaf node, you > would end up a substantial challenge resolving dependancies which would > create an Order(N) problem (i.e. there's a chance of excessive time to > complete the resolution). > > I certainly worked on some migration logic that took a similar approach to > this. > > > On Thursday, February 13, 2020 at 2:10:40 PM UTC, Adam Johnson wrote: >> >> I don’t think many people can answer this off the top of their heads. I >> certainly can’t and I have contributed a couple things to migrations. >> >> It’s probably quite necessary there’s only one leaf node but I can’t say >> for sure. >> >> On Thu, 13 Feb 2020 at 13:58, caio <caio....@gmail.com> wrote: >> >>> Cool. If I'm understanding this correctly, it auto-resolves during >>> *makemigrations*? >>> >>> I'm looking for something that could handle conflicts during the >>> *migrate* command, but I'm not sure if that's really possible. I guess >>> it depends on how intrinsic the single-leaf-node restriction is to the >>> whole migration system >>> >>> Thanks! >>> >>> Em terça-feira, 11 de fevereiro de 2020 16:22:16 UTC-3, jackotonye >>> escreveu: >>>> >>>> Definitely a plus one on auto resolving migrations a test package still >>>> in planning aims to solve this >>>> https://github.com/jackton1/django-migration-resolver-hook >>>> >>>> On Feb 11, 2020, at 1:42 PM, Caio Ariede <caio....@gmail.com> wrote: >>>> >>>> Hey folks, >>>> >>>> I was looking at the code used to detect conflicts in migrations [1]. >>>> It seems to use a very safe approach, by avoiding with multiple node leafs >>>> in the migration graph. >>>> >>>> While this is safe, I’ve been having some problems when it comes to >>>> scalability when having multiple migrations created in a short period of >>>> time (for the same app). >>>> >>>> Questions: >>>> >>>> 1. Are there any obvious impediments on improving the conflicts >>>> detection? >>>> 2. Does anyone have ideas on how to improve the conflict detection? >>>> (eg. going down from app-level to model-level detection) >>>> >>>> >>>> Thanks! >>>> >>>> >>>> [1] >>>> https://github.com/django/django/blob/e3f6e18513224c8ad081e5a19da641f49b0b43da/django/db/migrations/loader.py#L301-L313 >>>> >>>> <https://www.google.com/url?q=https%3A%2F%2Fgithub.com%2Fdjango%2Fdjango%2Fblob%2Fe3f6e18513224c8ad081e5a19da641f49b0b43da%2Fdjango%2Fdb%2Fmigrations%2Floader.py%23L301-L313&sa=D&sntz=1&usg=AFQjCNEx66DSnIBa3UITs1hO7Mwpk_cxgw> >>>> >>>> -- >>>> Caio Ariede >>>> caio....@gmail.com >>>> >>>> >>>> >>>> >>>> >>>> -- >>>> 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-d...@googlegroups.com. >>>> To view this discussion on the web visit >>>> https://groups.google.com/d/msgid/django-developers/FE717E60-7B66-4050-B233-20C47FBF6038%40gmail.com >>>> >>>> <https://groups.google.com/d/msgid/django-developers/FE717E60-7B66-4050-B233-20C47FBF6038%40gmail.com?utm_medium=email&utm_source=footer> >>>> . >>>> >>>> >>> -- >>> 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-d...@googlegroups.com. >>> To view this discussion on the web visit >>> https://groups.google.com/d/msgid/django-developers/31d78cfc-05bc-4bee-897b-3d9e2e502a3d%40googlegroups.com >>> >>> <https://groups.google.com/d/msgid/django-developers/31d78cfc-05bc-4bee-897b-3d9e2e502a3d%40googlegroups.com?utm_medium=email&utm_source=footer> >>> . >>> >> -- >> Adam >> > > -- > 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-d...@googlegroups.com <javascript:>. > To view this discussion on the web visit > https://groups.google.com/d/msgid/django-developers/bd688186-752b-4bf5-9340-5d9607d17038%40googlegroups.com > > <https://groups.google.com/d/msgid/django-developers/bd688186-752b-4bf5-9340-5d9607d17038%40googlegroups.com?utm_medium=email&utm_source=footer> > . > > > -- You received this message because you are subscribed to the Google Groups "Django developers (Contributions to Django itself)" group. 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