On Tuesday, November 29, 2016 at 4:10:38 AM UTC-8, Craig Kerstiens wrote: > > My company (Citus Data) is interested in sponsoring some Django work. In > particular work on support for composite primary keys. From what I > understand this wouldn't be the first time the work has been explored and > it sounds like it has a number of intricacies to it ( > https://github.com/django/deps/blob/master/draft/0191-composite-fields.rst > and > https://github.com/django/deps/blob/master/draft/0192-standalone-composite-fields.rst). > > Our hope here is that it would be done in line with something that could > eventually become part of an official Django release vs. a one-off work > around. > > While we know there's no guarantee of it being accepted, we'd love to find > someone with some knowledge of all the existing areas that would have to be > touched and has some experience contributing to Django core to improve that > likelihood. As part of the work, we would want the two existing DEPs to be > completed and work towards getting those accepted by the broader community. > And hopefully it goes without saying, but we'd fully expect all the work to > done in the open similar to other Django development. > > If you're interested in doing this work please reach out as we'd love to > discuss further. And if we have enough interest we'll be doing a full CFP > for the work to try to keep the process as fair as possible. >
Thank you Craig for bringing this up and for offering support. This is a long-wanted feature —the original ticket is 12 (!) years old— and as you know there has been extensive work done on this in the past, so it'd be great to find a way to push this all the way across the finish line. I just took a bit of time and tried to review all past discussions and implementations on the subject. See my recap and questions below. If anyone here on this list has any answers or thoughts about this, please jump in! I will then compile all new feedback and try to help move this forward. Composite fields DEPs ================== Currently the consensus as a first step is to finalize these two draft DEPs: https://github.com/django/deps/blob/master/draft/0191-composite-fields.rst https://github.com/django/deps/blob/master/draft/0192-standalone-composite-fields.rst Those drafts were written by Thomas Stephenson in 2015 and were discussed on this thread: https://groups.google.com/forum/#!topic/django-developers/MZUcOE6-7GY as well as in this pull request: https://github.com/django/deps/pull/12 It seems that some extra topics might need to be included and fleshed out in those DEPs, in particular: - Inspectdb integration - Migration implications - Form fields handling - Admin integration - Serialization/deserialization Some questions: - Do you agree that all the topics above should be covered in the DEPs? - Should other topics also be covered? - Are the current design details (observer pattern, lookup functions, constraints management, etc) already accepted or do they still need more discussion? Thomas had also started an implementation for these DEPs in this branch: https://github.com/ovangle/django/tree/dep_191 I've just merged current master into that branch and pushed it to my fork. You can see the details here: https://github.com/django/django/compare/eb97af0402536a86d5d8c916859986288bb88dc9...jphalip:dep_191 Some questions: - What is the status of this implementation work? - What are the pieces that still need to be implemented in order to fulfill the existing DEPs? - Is this implementation at a stage where it can formally be reviewed? If so I can create a PR to initiate a more detailed discussion. Composite primary keys (GSoC) ========================= Michal Petrucha participated in two Google Summer of Code (GSoC) projects in 2011 and 2013, during which some extensive code, tests and documentation were written. Unfortunately this project didn't reach the point where it could be merged into core and it eventually fell behind. Some relevant resources about these projects can be found here: - GSoC'2013 proposal: https://gist.github.com/koniiiik/5408673 - GSoC'2013 status updates: https://groups.google.com/forum/#!topic/django-developers/CD7OrkJ63zc - Discussion about some implementation details: https://github.com/django/django/pull/1407 - Status update from Michal from last year: https://groups.google.com/forum/#!topic/django-developers/SunyXc_BTVM Michal's implementation work is divided in two separate branches ("composite-fields" and "foreignkey-refactor"), presented below with their corresponding list of commits: "composite-fields" branch: - Branch: https://github.com/koniiiik/django/tree/soc2013/composite-fields - Commits: https://github.com/django/django/compare/041a076dadce547d450cf73d97401d63cde8891d...koniiiik:soc2013/composite-fields "foreign-refactor" branch: - Branch: https://github.com/koniiiik/django/tree/soc2013/foreignkey-refactor - Commits: https://github.com/django/django/compare/041a076dadce547d450cf73d97401d63cde8891d...koniiiik:soc2013/foreignkey-refactor I took a quick stab at merging current master into those branches but didn't make it too far as it turned out to be a little tedious. The main reason is that since 2013 there have been extensive changes in the ORM internals, in particular around the Meta api. So I'm not sure if it's worth doing that merge at this point. However, it'd be a shame to let all that great work go to waste and hopefully some of it can still be reused. Some questions: - Are there any portions of code or some solutions from Michal's implementation that could be ported over to the DEPs and to Thomas' more recent implementation? - What is the difference or relationship between the "composite-fields" and "foreignkey-refactor" branches? - Should a new DEP be submitted to specifically tackle composite primary keys and foreign keys? Other resources ============ Open tickets relating to this subject: - Original ticket for composite primary keys: https://code.djangoproject.com/ticket/373 - Support for Virtual Fields: https://code.djangoproject.com/ticket/16508 Third-party implementations of composite fields and composite primary keys: - https://github.com/simone/django-compositekey - https://github.com/vporton/django-composite-fields - https://bitbucket.org/bikeshedder/django-composite-field Other relevant links: - Out-dated Django wiki page: https://code.djangoproject.com/wiki/MultipleColumnPrimaryKeys - SQL Alchemy's PrimaryKeyConstraint API: http://docs.sqlalchemy.org/en/latest/core/constraints.html#sqlalchemy.schema.PrimaryKeyConstraint That's about it for now. Again, please anyone feel free to jump in with any questions or feedback, or if you're interested in contributing to this work. Thanks! 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