ruby-on-rails - Rails 5：ActiveRecord 使用 OR 条件查询连接表中的最后一个对象

Question

我需要一些帮助来查询这里（Rails 5.1）。我有一个名为Verification( belongs_to :verifiable, polymorphic: true) 的多态关联对象。其他对象，如Comment，可以有verifications( has_many :verifications, as: :verifiable)，最后一个（按 排序id）被认为是当前的。Verification有一个枚举属性status。我需要检索具有特定user_id（当前用户）或当前（即最后一个）验证对象且状态正确（例如，approved）的评论。

所以，我正在尝试：

self.where(user_id: user.id).or(self.joins(:verifications).limit(1).where(verifications: { status: 'approved' }))

但是 Rails 给了我以下错误：

Relation passed to #or must be structurally compatible. Incompatible values: [:joins, :references, :limit]

我该怎么办？

Answer 1

我无法使其仅在一个查询中起作用（我的 Arel 尝试失败）。所以希望以下内容就足够了（测试工作）：

latest_verification_ids = Verification.group(:verifiable_id).maximum(:id).values

# SELECT MAX("verifications"."id") AS maximum_id, "verifications"."verifiable_id" AS verifications_verifiable_id FROM "verifications" GROUP BY "verifications"."verifiable_id"

comments_whose_user_id_is_user_id_or_whose_last_verification_is_approved =
  Comment
    .where(user_id: user_id)
    .or(
      Comment.where(id:
        Comment.joins(:verifications)
          .where(
            verifications: {
              id: latest_verification_ids,
              status: 'approved'
            }
          )
      )
    )

# SELECT "comments".* FROM "comments" WHERE ("comments"."user_id" = ? OR "comments"."id" IN (SELECT "comments"."id" FROM "comments" INNER JOIN "verifications" ON "verifications"."verifiable_id" = "comments"."id" AND "verifications"."verifiable_type" = ? WHERE "verifications"."id" IN (4, 2) AND "verifications"."status" = ?))  [["user_id", 1], ["verifiable_type", "Comment"], ["status", "approved"]]