Question

project有legacy_users和group_users。 group_users必须通过groups才能获得users。我想构建一个project.users，将这些查询组合为一个arel。

以下是Project：

class Project < ActiveRecord::Base
  has_many    :project_accesses

  has_many    :groups,       through: :project_accesses, source: :group
  has_many    :legacy_users, through: :project_accesses, source: :user
  has_many    :group_users,  through: :groups, source: :users
end

这是Project.find(1).legacy_users的SQL：

SELECT "users".* FROM "users" INNER JOIN "project_accesses" ON "users"."id" =
"project_accesses"."user_id" WHERE "users"."deleted_at" IS NULL AND 
"project_accesses"."deleted_at" IS NULL AND "project_accesses"."project_id" = 1

这是Project.find(1).group_users的SQL：

SELECT "users".* FROM "users" INNER JOIN "group_memberships" ON "users"."id" =
"group_memberships"."user_id" INNER JOIN "groups" ON "group_memberships"."group_id" = 
"groups"."id" INNER JOIN "project_accesses" ON "groups"."id" = 
"project_accesses"."group_id" WHERE "users"."deleted_at" IS NULL AND 
"group_memberships"."deleted_at" IS NULL AND "groups"."deleted_at" IS NULL AND 
"project_accesses"."deleted_at" IS NULL AND "project_accesses"."project_id" = 1

只需在OR条件下添加INNER JOIN "project_accesses"即可获得我想要的内容。 Project.find(1).users：

SELECT "users".* FROM "users" INNER JOIN "group_memberships" ON "users"."id" = 
"group_memberships"."user_id" INNER JOIN "groups" ON "group_memberships"."group_id" = 
"groups"."id" INNER JOIN "project_accesses" ON ("groups"."id" = 
"project_accesses"."group_id" OR "users"."id" = "project_accesses"."user_id") WHERE 
"users"."deleted_at" IS NULL AND "group_memberships"."deleted_at" IS NULL AND 
"groups"."deleted_at" IS NULL AND "project_accesses"."deleted_at" IS NULL AND 
"project_accesses"."project_id" = 1

基本上我只是改为让查询做我想做的事：

INNER JOIN "project_accesses" ON ("groups"."id" = "project_accesses"."group_id" OR "users"."id" = "project_accesses"."user_id")

现在的问题是，这只是一个传递给find_by_sql的字符串，我无法弄清楚如何使它成为一个合适的Arel。

提前感谢您的帮助！

Answer 1

您应该可以使用ARel的joins方法手动构建您的联接，但仍然可以恢复实时关系。

http://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-joins

Answer 2

我越来越近了：

User.joins(:groups).joins("inner join project_accesses on (groups.id = 
project_accesses.group_id or users.id = project_accesses.user_id)").
where(project_accesses: {project_id:1}).merge(Group.scoped).
merge(GroupMembership.scoped).merge(ProjectAccess.scoped).uniq

有没有办法在Arel中写这个部分？

joins("inner join project_accesses on (groups.id = 
project_accesses.group_id or users.id = project_accesses.user_id)")

此外，是否有办法自动包含所有已加入模型的默认范围，以避免：

.merge(Group.scoped).merge(GroupMembership.scoped).merge(ProjectAccess.scoped)

有查询工作，但想要ActiveRelation

2 个答案: