How to write Activerecord/Arel intersection query

问题

I got this working in PSQL:

SELECT "profiles".id FROM "profiles"
INNER JOIN "integration_profiles"
ON "integration_profiles"."profile_id" = "profiles"."id"
INNER JOIN "integrations"
ON "integrations"."id" = "integration_profiles"."integration_id"
WHERE "integrations"."provider" = 'csv'
INTERSECT
SELECT "profiles".id FROM "profiles"
INNER JOIN "integration_profiles"
ON "integration_profiles"."profile_id" = "profiles"."id"
INNER JOIN "integrations"
ON "integrations"."id" = "integration_profiles"."integration_id"
WHERE "integrations"."provider" = 'kickstarter'

I'd like to convert it to ActiveRecord query or Arel.

I tried:

Arel::Nodes::Intersect.new(
  Profile.joins(:integrations).where(integrations: { provider: 'csv' }),
  Profile.joins(:integrations).where(integrations: { provider: 'kickstarter' })
)

[Debug]   Profile Load (408.2ms)  SELECT "profiles".* FROM "profiles" INNER JOIN "integration_profiles" ON "integration_profiles"."profile_id" = "profiles"."id" INNER JOIN "integrations" ON "integrations"."id" = "integration_profiles"."integration_id" WHERE "integrations"."provider" = 'csv' (pid:65570)
 [Debug]   Profile Load (1.9ms)  SELECT "profiles".* FROM "profiles" INNER JOIN "integration_profiles" ON "integration_profiles"."profile_id" = "profiles"."id" INNER JOIN "integrations" ON "integrations"."id" = "integration_profiles"."integration_id" WHERE "integrations"."provider" = 'kickstarter' (pid:65570)

This works:

ps = (
  Profile.select(:id)
    .joins(:integrations)
    .where(integrations: { provider: 'csv' })
    .intersect(
      Profile.select(:id)
        .joins(:integrations)
        .where(integrations: {provider: 'kickstarter'})
    )
)
Profile.from(Profile.arel_table.create_table_alias(ps, :profiles))

Is there a way to get it done in one step? Or a way to get the ps to output the results instead it just outputs an Arel object...

回答1:

You can join 2 times integration_profiles and integrations like this:

Profile
  .joins("INNER JOIN integration_profiles AS ip_csv ON ip_csv.profile_id = profiles.id")
  .joins("INNER JOIN integrations AS i_csv ON i_csv.id = ip_csv.integration_id")
  .joins("INNER JOIN integration_profiles AS ip_kickstarter ON ip_kickstarter.profile_id = profiles.id")
  .joins("INNER JOIN integrations AS i_kickstarter ON i_kickstarter.id = ip_kickstarter.integration_id")
  .where("i_csv.provider='csv' AND i_kickstarter.provider='kickstarter'")
  .pluck("profiles.id")

If you want a more readable query, define two scopes like this:

class Profile < ActiveRecord::Base
  has_many :integration_profiles
  has_many :integrations, through: :integration_profiles

  scope :csv,         ->{joins(:integrations).where(integrations: { provider: 'csv' })}
  scope :kickstarter, ->{joins(:integrations).where(integrations: { provider: 'kickstarter' })}
end

And then:

Profile.csv.where(id: Profile.kickstarter.pluck(:id) ).pluck(:id)

You will end up with 2 queries but this reads much better.

SELECT "profiles"."id" FROM "profiles"
INNER JOIN "integration_profiles" ON "integration_profiles"."profile_id" = "profiles"."id" 
INNER JOIN "integrations" ON "integrations"."id" = "integration_profiles"."integration_id" 
WHERE "integrations"."provider" = 'kickstarter'

SELECT "profiles"."id" FROM "profiles"
INNER JOIN "integration_profiles" ON "integration_profiles"."profile_id" = "profiles"."id" 
INNER JOIN "integrations" ON "integrations"."id" = "integration_profiles"."integration_id" 
WHERE "integrations"."provider" = 'csv' AND "profiles"."id" IN (1, 3)

If you want only the ids for profiles you can take another path: extract profile_id from integration_profiles:

class Integration < ActiveRecord::Base
  has_many :integration_profiles
  has_many :profiles, through: :integration_profiles

  scope :csv,         -> { where(provider: 'csv') }
  scope :kickstarter, -> { where(provider: 'kickstarter') }
end

class IntegrationProfile < ActiveRecord::Base
  belongs_to :integration
  belongs_to :profile
end

IntegrationProfile.joins(:integration).csv.where(
  profile_id: IntegrationProfile.joins(:integration).kickstarter.pluck(:profile_id)
).pluck(:profile_id)

This will still generate 2 queries, but those are simpler:

SELECT "integration_profiles"."profile_id" FROM "integration_profiles"
INNER JOIN "integrations" ON "integrations"."id" = "integration_profiles"."integration_id" 
WHERE "integrations"."provider" = 'kickstarter'

SELECT "integration_profiles"."profile_id" FROM "integration_profiles"
INNER JOIN "integrations" ON "integrations"."id" = "integration_profiles"."integration_id" 
WHERE "integrations"."provider" = 'csv' AND "integration_profiles"."profile_id" IN (1, 3)

来源：https://stackoverflow.com/questions/24320469/how-to-write-activerecord-arel-intersection-query

标签

ruby-on-rails

activerecord