Feeding eq_any an empty list (eventually) breaks.

[cqfd]

Feeding eq_any an empty list doesn't behave very well: you get back an Arel::Nodes::Grouping whose @expr is nil. Calling to_sql will then throw a RuntimeError: unsupported: NilClass exception.

It would be great if Arel could return an empty/impossible relation here. If that's not possible, I would much rather have eq_any throw right away rather than waiting for to_sql to blow up.

[danielpclark]

BUMP

eq_any works in Arel 5 and accepts empty collections and likewise works in returning empty collections. As of Arel 6 this no longer works. Both:

eq_any(nil)
eq_any([])

Raise:

RuntimeError: unsupported: NilClass

[sgrif]

Thanks but I don't think we need to support this use case. As you mentioned, it changed in a major version bump.

[danielpclark]

This is an important use case. I use it in geo_location lookup with addresses.

events = Event.where(
  Event.arel_table[:eventable_type].eq("User").
    and(Event.arel_table[:eventable_id].eq(current_user.id).or(
      Event.open.where_values.first.and(
        Event.arel_table[:id].eq_any(
          Address.where(addressable_type: "Event").
          where.not(addressable_id: current_user.events.ids).
          near(
            current_user.current_addresses.first.try(&:geo_locale),
            300
          ).select(&:addressable_id)
        )
      )
    )
  )
)

This query pulls up events that the user has created and any near the user. By not having eq_any support empty results, and having it raise an error, you break standard behavior that ActiveRecord and other Arel methods still conform to. I don't see why it's important to have a breaking change like this when expecting empty results is a given in any situation.

[sgrif]

The use of Arel from Active Record is not supported. It is an internal, private API.

[danielpclark]

So the wonderfully made conference talks on using Arel for ActiveRecord queries were misinformed?

[sgrif]

Or maybe just missing the caveat that like any private API, it may break
between versions.

On Sun, Oct 4, 2015, 8:04 AM Daniel P. Clark notifications@github.com
wrote:

So the wonderfully made conference talks on using Arel for ActiveRecord
queries were misinformed?

—
Reply to this email directly or view it on GitHub
#368 (comment).

[jfeldstein]

Love the fact that in open source you can just fix the issue. Boom.

Thanks for making the sane choice: eq_any an empty set == no results, not a crash.

[danielpclark]

@jfeldstein The patch was only given for the test suite in Arel 5 for the Rails 4.1 series. After Rails 4.1 it will crash on an empty set. If you want to avoid this issue with later versions of Rails you can write your own method:

module ::Arel
  module Predications
    def eql_any others
      if others.length.zero?
        Nodes::SqlLiteral.new "(NULL)"
      else
        grouping_any :eq, others
      end
    end
  end
end

[jfeldstein]

Much obliged.