Experiment has_many :features 
Feature belongs_to :experiment

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

@H_301_4@我希望这会返回每个功能的ID和实验的ID.

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

@H_301_4@相反,这将返回实验的ID,然后返回nil

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

@H_301_4@这有三个方面很奇怪：

@H_301_4@>即使它是一个内连接,只返回一个实验,我能够从功能中提取列(features.name)
>一切都很好,直到重复列名称.
>首先报告最后一个弹出列,就好像第一列被覆盖一样.切换拔除顺序会切换返回值.

@H_301_4@这似乎是一个错误,但也许我做错了什么.有小费吗？

@H_301_4@sql输出：

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

@H_301_4@注意.这是一个与查询类似的简化问题：

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

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

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