ActiveRecord 和 Arel (SQL) 的过滤链问题

Question

设置如下：

class Title
  has_many :managed_rights
end

class ManagedRight
  belongs_to :title
  has_many :managed_right_countries
  enumerize :territory_rights, in: [:all, :include, :exclude], default: :all
end

class ManagedRightCountry
  belongs_to :managed_right
  belongs_to :country
end

class Country; end

我想按国家/地区过滤标题，其中country_ids = [3, 5, 8, 9]。

• 所有案例 如果title.managed_rights[0].territory_rights == :all选择这个标题
• 如果包含大小写 仅当 managed_right_countries 中的任何一个在 country_ids 中时才选择，否则跳过。

title.managed_rights[0].territory_rights == :include 
AND title.managed_rights[0].managed_right_countries IN country_ids

• 如果排除案例 选择所有标题，除非 managed_right_countries 中的任何一个在 country_ids 中。

title.managed_rights[0].territory_rights == :exclude
AND title.managed_rights[0].managed_right_countries ALL NOT IN country_ids

这就是我对 Arel 的尝试：

managed_rights = ManagedRight.arel_table
managed_right_countries = ManagedRightCountry.arel_table

Title.left_outer_joins(managed_rights: :managed_right_countries)
  .where(
    # some other filters not related to "managed_rights"
    managed_rights[:territory_rights].eq(:all)
      .or(
        managed_rights[:territory_rights].eq(:include)
        .and(managed_right_countries[:country_id].in(country_ids))
        .or(
          managed_rights[:territory_rights].eq(:exclude)
          .and(managed_right_countries[:country_id].not_in(country_ids))
        )
      )
  ).distinct

它适用于大多数情况，除非managed_right_countries.country_id 有一些不在country_ids 数组中的ID。上面的查询 :exclude 的含义仅在所有国家/地区都在数组中时才有效。 但是如果数组中有任何国家，我需要从结果中排除标题。

我怎样才能让它正常工作？

最好使用 AREL，但如果无法仅使用 Arel，原始 SQL(PostgreSQL) 也可以工作。

示例：

title_01 has `managed_rights[0].territory_rights = :all`
title_02 has `managed_rights[0].territory_rights = :include`
         and `managed_rights[0].managed_right_countries = [1, 2]`
title_03 has `managed_rights[0].territory_rights = :exclude`
         and `managed_rights[0].managed_right_countries = [2, 3]`

• 当按国家 [1] 过滤时，应选择所有 3 个标题（title_02 包含 1 个，但 title_03 不排除）
• 当按国家 [2] 时，仅应选择 title_01 和 title_02（因为排除了三分之三）
• 当按国家 [3] 时，仅应选择 title_01，因为 title_02 不包括 3，而 title_03 不包括 3
• 如果按空国家/地区过滤 []，则应显示所有三个

Answer 1

通过创建嵌套子查询来解决。

SQL解决方案：

SELECT titles.* FROM titles
LEFT OUTER JOIN managed_rights ON managed_rights.title_id = titles.id
LEFT OUTER JOIN managed_right_countries ON managed_right_countries.managed_right_id = managed_rights.id
WHERE (titles.rights = 'all' OR managed_rights.title_id is NULL)
OR managed_rights.territory_rights = 'all'
OR (
    managed_rights.territory_rights = 'include' AND managed_right_countries.country_id in (country_ids)
)
OR (
    managed_rights.territory_rights = 'exclude' 
        AND NOT titles.id in (
            SELECT titles.id FROM titles
            LEFT OUTER JOIN managed_rights ON managed_rights.title_id = titles.id
            LEFT OUTER JOIN managed_right_countries ON managed_right_countries.managed_right_id = managed_rights.id
            WHERE managed_rights.territory_rights = 'exclude' 
                AND managed_right_countries.country_id in (country_ids)
        )
)

AREL 解决方案：

titles = Title.arel_table
managed_rights = ManagedRight.arel_table
managed_right_countries = ManagedRightCountry.arel_table

excluded_title_ids = titles.project('titles.id')
  .join(managed_rights, Arel::Nodes::OuterJoin)
  .on(managed_rights[:title_id].eq(titles[:id]))
  .join(managed_right_countries, Arel::Nodes::OuterJoin)
  .on(managed_right_countries[:managed_right_id].eq(managed_rights[:id]))
  .where(
    managed_rights[:territory_rights].eq(:exclude)
      .and(managed_right_countries[:country_id].in(available_countries))
  )

Title.left_outer_joins(managed_rights: :managed_right_countries)
  .where(
    managed_rights[:territory_rights].eq(:all)
    .or(
      managed_rights[:territory_rights].eq(:include)
        .and(managed_right_countries[:country_id].in(available_countries))
        .or(
          managed_rights[:territory_rights].eq(:exclude)
          .and(titles[:id].not_in(excluded_title_ids))
        )
    )
  )