IME, which subset of features you use largely depends on the industry sector you're in. There are many rails features I haven't used in the past decade of working on rails apps, but they are important to some users. CTEs are primarily useful when dealing with much larger databases and complex schemas. There are very few rails codebases old enough to have developed a highly-complex schema because rails isn't very old. However, as more rails applications become large and long-established, this feature will affect more developers. As a result, I think that at some point this will become an important feature. Whether it belongs in core right now hinges (imo) primarily on how much complexity the implementation adds. I've had a read through the postgres_ext functionality to add CTEs; it's 80 lines of very straightforward code which should work unmodified for mysql 8+, sqlite 3.8.3+, oracle, frontbase, IBM DB, and MS SQL server. There'll be a bit of extra work to make Relation::Merger#merge work correctly - alongside merge_multi_values and merge_clauses etc, we'd have to add merge_ctes. Relation::QueryMethods#build_arel and Relation::Merger#merge are the only places anyone not working on CTEs would notice that this change exists. Thanks, Daniel Heath
On Wed, Jan 16, 2019, at 11:58 AM, Rafael Mendonça França wrote: > Cool! I think the hard work is already done. But I still find it hard > to justify this in the framework. It is a feature that is out of Rails > for more than 10 years and I personally never needed it working in > many applications through the years so I'm not sure if I want to add > that complexity to the framework and maintain this feature.> > We are planing to expose arel as public API sometime in the future so > maybe that would be enough to allow people who wants to use CTE to be > able to use in their application.> > Rafael Mendonça França > http://twitter.com/rafaelfranca > https://github.com/rafaelfranca > > > On Tue, Jan 15, 2019 at 7:41 PM Sean Linsley > <sean.ian.lins...@gmail.com> wrote:>> While we’re on the subject, I have a PR > to get postgres_ext working >> with Rails 5.2, but need help from someone that has experience with >> Arel’s internals.>> >> https://github.com/danmcclain/postgres_ext/pull/2 >> >> Though more broadly I’m of the opinion that most of it should be >> inlined into Rails, and would be happy to work on that effort if it’s >> welcome.>> >>> On Jan 15, 2019, at 6:37 PM, Daniel Heath <daniel.r.he...@gmail.com> >>> wrote:>>> >>> https://rubygems.org/gems/postgres_ext implements this for rails up >>> to version 4, and has ~2 million downloads.>>> >>> https://github.com/kmurph73/ctes_in_my_pg ports the code to rails 5.>>> >>> There are also numerous blog posts around documenting how to work >>> around the issue by dropping down to raw Arel or string >>> interpolation.>>> >>> eg: >>> * >>> http://www.scimedsolutions.com/articles/75-arel-part-ii-common-table-expressions>>> >>> * https://hashrocket.com/blog/posts/recursive-sql-in-activerecord >>> * >>> https://sonnym.github.io/2017/06/05/common-table-expressions-in-activerecord-a-case-study-of-quantiles/>>> >>> >>> >>> https://www.cockroachlabs.com/blog/cockroachdb-hearts-activerecord-ruby-on-rails/ >>> also mentions that ActiveRecord uses CTEs internally.>>> >>> Would you agree that's a suitable level of usage to justify >>> including this SQL-99 feature in core ActiveRecord? Or is the >>> complexity likely to be too much for the number of users affected?>>> >>> Thanks, >>> >>> Daniel Heath >>> >>> On Wednesday, January 16, 2019 at 11:21:42 AM UTC+11, Rafael >>> Mendonça França wrote:>>>> Thank you for the feature proposal. It doesn't >>> seem to be difficult >>>> to implement this as a gem given most of the APIs you need in able >>>> to implement something like this are public.>>>> >>>> What do you think about implementing this first as a gem and see if >>>> there are adoption of this feature before proposing adding to the >>>> rails framework?>>>> >>>> Thanks. >>>> >>>> Rafael Mendonça França >>>> http://twitter.com/rafaelfranca >>>> https://github.com/rafaelfranca >>>> >>>> >>>> On Tue, Jan 15, 2019 at 7:12 PM Daniel Heath <daniel....@gmail.com> >>>> wrote:>>>>> I'd like to be able to use my ActiveRecord scopes in a CTE for >>>>> another scope.>>>>> >>>>> Proposed syntax >>>>> >>>>> >>>>> class Post < ActiveRecord::Base has_many :comments end >>>>> >>>>> class Comment < ActiveRecord::Base belongs_to :post end >>>>> >>>>> Post.with(Comment.select(:post_id), name: :post_ids, recursive: >>>>> false).where(id: {post_ids: :post_id}) >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>>>>>>> Would a patch supporting this syntax be accepted? >>>>> >>>>> Thanks, >>>>> >>>>> Daniel Heath >>>>> >>>>> -- >>>>> You received this message because you are subscribed to the >>>>> Google Groups "Ruby on Rails: Core" group.>>>>> To unsubscribe from >>>>> this group and stop receiving emails from it, >>>>> send an email to rubyonrails-co...@googlegroups.com.>>>>> To post to >>>>> this group, send email to >>>>> rubyonra...@googlegroups.com.>>>>> Visit this group at >>>>> https://groups.google.com/group/rubyonrails-core.>>>>> For more >>>>> options, visit https://groups.google.com/d/optout. >>> >>> -- >>> You received this message because you are subscribed to the Google >>> Groups "Ruby on Rails: Core" group.>>> To unsubscribe from this group and >>> stop receiving emails from it, >>> send an email to rubyonrails-core+unsubscr...@googlegroups.com.>>> To >>> post to this group, send email to rubyonrails- >>> c...@googlegroups.com.>>> Visit this group at >>> https://groups.google.com/group/rubyonrails-core.>>> For more options, >>> visit https://groups.google.com/d/optout. >> >> >> -- >> You received this message because you are subscribed to the Google >> Groups "Ruby on Rails: Core" group.>> To unsubscribe from this group and >> stop receiving emails from it, >> send an email to rubyonrails-core+unsubscr...@googlegroups.com.>> To post >> to this group, send email to rubyonrails- >> c...@googlegroups.com.>> Visit this group at >> https://groups.google.com/group/rubyonrails-core.>> For more options, >> visit https://groups.google.com/d/optout. > > -- > You received this message because you are subscribed to the Google > Groups "Ruby on Rails: Core" group.> To unsubscribe from this group and > stop receiving emails from it, > send an email to rubyonrails-core+unsubscr...@googlegroups.com.> To post to > this group, send email to rubyonrails- > c...@googlegroups.com.> Visit this group at > https://groups.google.com/group/rubyonrails-core.> For more options, visit > https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Core" group. 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