Add prepend_order as a new query method to prepend the specified order onto any existing order

[agrobbin]

Summary

I recently ran into a situation where it would've been great to prepend a new ORDER BY clause to a query. In our case, it was when using a scope that itself had something to the effect of:

class Profile < ApplicationRecord
  belongs_to :user

  scope :recently_updated, -> { where(arel_table[:updated_at].gteq(7.days.ago)).order(updated_at: :desc) }
end

class User < ApplicationRecord
  has_one :profile

  scope :recently_updated, -> { joins(:profile).merge(Profile.recently_updated) }
end

We wanted to use User.recently_updated, but needed to put a specific group of users at the top of the list. The only way to do that without something like prepend_order would be to reimplement the recently_updated scopes defined on the model.

With prepend_order, we can simply call User.recently_updated.prepend_order('...'), and we're done!

Another way we could use this would be in conjunction with ActiveRecord::FinderMethods#ordered_relation:

class CustomerLegalEntity < ApplicationRecord
  scope :ordered, -> { ordered_relation.prepend_order(default: :desc) }
end

[p8]

Hi @agrobbin. Thanks for the PR.
There already is a method (with almost the same name): reorder https://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-reorder

   User.order('email DESC').reorder('id ASC') # generated SQL has 'ORDER BY id ASC'

[agrobbin]

@p8 I looked at reorder, and that's not quite the same as this:

User.order('email DESC').reorder('id ASC') # generated SQL has `ORDER BY id ASC`
User.order('email DESC').preorder('id ASC') # generated SQL has `ORDER BY id ASC, email DESC`

[p8]

@agrobbin Ah that makes sense.

[simi]

🤔 my initial idea regarding this was to provide block to reorder with current order as a argument to be able to enhance it. preorder can just use this as well.

[agrobbin]

@simi I'm definitely open to other approaches here, this just felt like the simplest one with the least likelihood of impacting existing applications! I bet we could achieve the same result by changing reorder to optionally accept a block, but there was something nice about keeping the interface here identical to the other AR query methods, and not changing the existing implementation of any of the other query methods.

[rails-bot]

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs.
Thank you for your contributions.

[agrobbin]

I'd love to get some input on this contribution if anyone from the core team has some time!

[rails-bot]

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs.
Thank you for your contributions.

[ghiculescu]

@p8 I looked at reorder, and that's not quite the same as this:

User.order('email DESC').reorder('id ASC') # generated SQL has `ORDER BY id ASC`
User.order('email DESC').preorder('id ASC') # generated SQL has `ORDER BY id ASC, email DESC`

I think in this case you'd want to do

User.order('email DESC').reorder('ORDER BY id ASC, email DESC')

I don't mind this new addition. My main concern is the name. To me preorder looks like a typo of reorder.

[agrobbin]

@ghiculescu I'm totally open to a different name! I do like the simplicity of order, reorder, and preorder, but I see the concern about potential typos. A more ... expressive term could be prefix_order, or something else!

[rails-bot]

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs.
Thank you for your contributions.

[agrobbin]

I'd still love to get some 👀 on this for potential inclusion!

[rails-bot]

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs.
Thank you for your contributions.

[agrobbin]

I'd still love to get this into Rails core!

[rails-bot]

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs.
Thank you for your contributions.

[agrobbin]

I'd still love to get this into Rails core!

[p8]

@agrobbin Maybe prepend_order would be a clearer name? Similar to reverse_order…

[agrobbin]

@p8 updated! I've also rebased off of the latest main, to resolve the outstanding merge conflicts.

[p8]

Thanks @agrobbin !
Looking at similar PR's it seems like similar PR's were rejected 😞 but that was a long time ago...
#16051 Provide prepend_order and append_order relation methods
#18245 Adding preorder to change order presedence

[agrobbin]

I hadn't seen those @p8! I'm hopeful there is openness to this feature now, particularly since based on what was said back in #16051, the opposition wasn't to the feature itself but to the changing of the default over time. Since this is purely additive, I've got my 🤞🏻 that this is acceptable! If order.prepend is more palatable than prepend_order, I'm happy to change it to that. I'm not sure if it is perfectly symmetrical with WHERE NOT, but I definitely get the interest in that kind of DSL. Let me know what you'd suggest!

[agrobbin]

@p8 I know it's been awhile (actually, almost exactly a year!), but I'm wondering if you have a few moments to take another look at this.