ruby-on-rails - rails : how do I unscope a uniq call?

Question

我有一个关系，其中 uniq 被调用为:

rel = Car.where(brand: 'Audi').order(:price).uniq

现在我想取消 uniq (DISTINCT) 部分的作用域，这样我就可以:

rel.limit(30).pluck(:id)

因为这会给我这样的错误:

ActiveRecord::StatementInvalid: PG::InvalidColumnReference: ERROR: for SELECT DISTINCT, ORDER BY expressions must appear in select list

这是由于查询调用:SELECT DISTINCT(id) FROM cars WHERE brand = 'Audi' ORDER BY price 我希望它执行的操作是:SELECT id FROM cars WHERE brand = 'Audi' ORDER BY price - 但是我无法弄清楚如何仅取消停止 DISTINCT 部分？

Answer 1

您可以使用 distinct(false) 来覆盖 uniq:

rel = Car.where(brand: 'Audi').order(:price).uniq
rel.distinct(false).limit(30).pluck(:id)