Hello Pavel, Sorry for the delay in my answer.
Unfortunately I don't know django.db.migrations very well and I won't be able to help you with the details of a patch in this area. I still think improving support for zero downtime migrations would be worthwhile. Writing a proposition in a ticket (or, if you're feeling really ambition, in a DEP) would be a good way to start. Sorry I can't help more! Best regards, -- Aymeric. > On 7 Oct 2018, at 20:53, pavel.tysla...@gmail.com wrote: > > Hello, Aymeric > > Thanks for your reply. > > CREATE INDEX CONCURRENTLY is a big part for zero downtime migrations support, > but there are too many additional questions as should ALTER TABLE ADD COLUMN > UNIQUE splitted to CREATE INDEX and constraint creation or should be handled > FOREGN KEY, CHECK and NOT NULL constraints creation that can take ACCESS > EXCLUSIVE for long time on huge table or is it accessible to avoid > transactions in highlighted above cases? > > Unfortunately I don't know what direction django planned to develop, so I can > go different ways without support. > > Is it a good idea to create ticket about zero downtime migrations support > with detailed proposition of improvements and backward compatibility support? > > Regards, Paveł > > On Sunday, 7 October 2018 10:31:27 UTC+3, Aymeric Augustin wrote: > Hello Pavel, > > There's an accepted ticket about CREATE INDEX CONCURRENTLY: > https://code.djangoproject.com/ticket/21039 > <https://code.djangoproject.com/ticket/21039>. A concrete proposal for adding > this feature to Django would be interesting. > > I'm not really sure about your two other suggestions. If you think they're > improving the PostgreSQL backend, you're welcome to create a ticket and > propose a pull request. > > Keep in mind backwards-compatibility if changes are improvements in your use > case but perhaps not for everyone else. For example, it may be better that > index creating remain an atomic operation (so, not concurrent) by default. > > Best regards, > > -- > Aymeric. > > > >> On 26 Sep 2018, at 07:41, pavel.t...@ <>gmail.com <http://gmail.com/> wrote: >> >> Hi, >> >> I found that django migrations don't designed for live updates on large >> tables for postgres, eg. index creation doesn't use concurrently or alter >> table operation can take ACCESS EXCLUSIVE lock for long time. >> >> Before I mostly wrote custom migrations, but after one of downtime I decided >> to avoid most common cases at all and wrote postgres backend that helps me >> in it: https://github.com/tbicr/django-pg-zero-downtime-migrations >> <https://github.com/tbicr/django-pg-zero-downtime-migrations>. When I wrote >> it I found that it's a pretty easy extend core postgres backend, but a few >> things required rewrite on my side: >> >> - >> https://github.com/django/django/blob/master/django/db/backends/base/schema.py#L152 >> >> <https://github.com/django/django/blob/master/django/db/backends/base/schema.py#L152> >> used both for table columns creation and altering table add column, but not >> null constraint and index constraints can't be changed without whole method >> rewriting >> - for one core sql statement I found more "safe" equivalent with two sql >> statements, but it's a bit hard to execute it, for example more save create >> invalid constraint and than validate it or create concurrently index and >> than create unique constraint >> >> also I found that not all constraint names quoted in generated sql, for >> example add_unique_together got `ALTER TABLE "table_name" ADD CONSTRAINT >> table_name_f1_f2_hash_uniq UNIQUE ("f1", "f2")`, but expected `ALTER TABLE >> "table_name" ADD CONSTRAINT "table_name_f1_f2_hash_uniq" UNIQUE ("f1", "f2")` >> >> So I just curious is anybody interested to make django migrations more >> reliable for large tables in prod or interested in some improvements >> highlighted above, that can simplify writing backends for this purpose? >> >> I also will be appreciated if somebody can share another solutions for this >> purpose. >> >> Paveł >> >> -- >> 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-develop...@ <>googlegroups.com <http://googlegroups.com/>. >> To post to this group, send email to django-d...@ <>googlegroups.com >> <http://googlegroups.com/>. >> Visit this group at https://groups.google.com/group/django-developers >> <https://groups.google.com/group/django-developers>. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/django-developers/421f001b-ca11-42bf-8735-0c6947b41988%40googlegroups.com >> >> <https://groups.google.com/d/msgid/django-developers/421f001b-ca11-42bf-8735-0c6947b41988%40googlegroups.com?utm_medium=email&utm_source=footer>. >> For more options, visit https://groups.google.com/d/optout >> <https://groups.google.com/d/optout>. > > > -- > 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 > <mailto:django-developers+unsubscr...@googlegroups.com>. > To post to this group, send email to django-developers@googlegroups.com > <mailto:django-developers@googlegroups.com>. > Visit this group at https://groups.google.com/group/django-developers > <https://groups.google.com/group/django-developers>. > To view this discussion on the web visit > https://groups.google.com/d/msgid/django-developers/c14b53e6-3995-4c21-9993-dcaf8e22b825%40googlegroups.com > > <https://groups.google.com/d/msgid/django-developers/c14b53e6-3995-4c21-9993-dcaf8e22b825%40googlegroups.com?utm_medium=email&utm_source=footer>. > For more options, visit https://groups.google.com/d/optout > <https://groups.google.com/d/optout>. -- You received this message because you are subscribed to the Google Groups "Django developers (Contributions to Django itself)" group. 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