Rails ".pluck" on joined tables with columns of the same name returns one value and then nil

Question

Experiment has_many :features 
Feature belongs_to :experiment

Experiment.where("experiments.id=1")
    .joins(:features)
    .pluck("features.id", "experiments.id")

I expect this to return the id of each features and the id of the experiment.

[
    [1, 1],
    [2, 1],
    [3, 1],
    # ....
]

Instead this returns the id of the experiment and then nil

[
    [1, nil],
    [1, nil],
    [1, nil],
    # ....
]

This is strange in three regards:

• even though it is an inner join and only an Experiment is returned I am able to pluck columns from features (features.name)
• everything is fine until a column name is repeated.
• the last plucked column is reported first, as if the first column is overwritten. Switching the order of pluck switches the returned value.

This seems like a bug but maybe I am doing something wrong. Any tips?

SQL output:

SELECT features.id, experiments.id FROM "experiments" INNER JOIN "features" ON "features"."experiment_id" = "experiments"."id" WHERE (experiments.id=1)

Note. This is a simplified question pertaining to a query looking like:

Experiment.where("experiments.id=1")
    .joins(feature: { child2: { :child3 } })
    .pluck("feature.id, child3.id")

Answer 1

This is a bit tricky. Since there's an INNER JOIN the query produces only one id in this instance. You can actually form query the other way around:

Feature.joins(:experiment)
       .where(features: { experiment_id: 1 })
       .pluck(:id, :experiment_id)

Or:

Feature.joins(:experiment)
       .where(experiments: { id: 1 })
       .pluck(:id, :experiment_id)