refactor: make member_email_deliveries a typed log

app/mailers/concerns/email_delivery.rb

@@ -3,18 +3,20 @@ module EmailDelivery
 
   private
 
+  # The mailer action name distinguishes which email a logged row is for.
+  # find_or_create_by keeps a replayed delivery (e.g. a retried job) from
+  # raising on the unique index after the email has already gone out.
   def log_sent_email
     member = params[:member]
     return unless member
     return unless @_mail_was_called
 
-    MemberEmailDelivery.create!(
-      member: member,
-      subject: mail.subject,
-      body: mail.html_part ? mail.html_part.body.to_s : mail.body.to_s,
-      to: Array(mail.to),
-      cc: Array(mail.cc),
-      bcc: Array(mail.bcc)
-    )
+    MemberEmailDelivery.find_or_create_by!(member:, email_type: action_name) do |delivery|
+      delivery.subject = mail.subject
+      delivery.body = mail.html_part ? mail.html_part.body.to_s : mail.body.to_s
+      delivery.to = Array(mail.to)
+      delivery.cc = Array(mail.cc)
+      delivery.bcc = Array(mail.bcc)
+    end
   end
 end

app/services/three_month_email_service.rb

@@ -21,8 +21,7 @@ def self.send_chaser
                     .accepted_toc
                     .joins(:groups)
                     .merge(Group.students)
-                    .left_joins(:member_email_deliveries)
-                    .where(member_email_deliveries: { id: nil })
+                    .where.not(id: MemberEmailDelivery.where(email_type: 'chaser').select(:member_id))
                     .where.not(id: recent_attendee_ids)
                     .where(id: past_year_attendee_ids)
                     .distinct

db/migrate/20260831100000_add_email_type_to_member_email_deliveries.rb

@@ -0,0 +1,8 @@
+class AddEmailTypeToMemberEmailDeliveries < ActiveRecord::Migration[8.1]
+  def change
+    # 'chaser' backfills existing rows (the only mailer action logging today);
+    # the default is then dropped so every writer must set the type explicitly.
+    add_column :member_email_deliveries, :email_type, :string, default: 'chaser', null: false
+    change_column_default :member_email_deliveries, :email_type, from: 'chaser', to: nil
+  end
+end

db/migrate/20260831100100_add_unique_index_on_member_email_deliveries_member_and_type.rb

@@ -0,0 +1,7 @@
+class AddUniqueIndexOnMemberEmailDeliveriesMemberAndType < ActiveRecord::Migration[8.1]
+  disable_ddl_transaction!
+
+  def change
+    add_index :member_email_deliveries, %i[member_id email_type], unique: true, algorithm: :concurrently
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[8.1].define(version: 2026_08_31_090000) do
+ActiveRecord::Schema[8.1].define(version: 2026_08_31_100100) do
   # These are extensions that must be enabled in order to support this database
   enable_extension "pg_catalog.plpgsql"
 
@@ -420,10 +420,12 @@
     t.text "body"
     t.text "cc", default: [], array: true
     t.datetime "created_at", null: false
+    t.string "email_type", null: false
     t.bigint "member_id"
     t.text "subject"
     t.text "to", default: [], array: true
     t.datetime "updated_at", null: false
+    t.index ["member_id", "email_type"], name: "index_member_email_deliveries_on_member_id_and_email_type", unique: true
     t.index ["member_id"], name: "index_member_email_deliveries_on_member_id"
   end
 

spec/fabricators/member_email_delivery_fabricator.rb

@@ -1,5 +1,6 @@
 Fabricator(:member_email_delivery) do
   member(fabricator: :member)
+  email_type('chaser')
   subject('Chaser')
   body('Lorem ipsum')
   to(['test_email@address'])

spec/mailers/member_mailer_spec.rb

@@ -180,12 +180,20 @@
       log = MemberEmailDelivery.last!
 
       expect(log.member).to eq(member)
+      expect(log.email_type).to eq('chaser')
       expect(log.subject).to eq('It’s been a while, how are you doing? ♥️')
       expect(log.to).to eq([member.email])
       # premailer-rails converts the message to multipart/alternative during
       # delivery, so the logged body must come from the html part
       expect(log.body).to be_present
       expect(log.body).to include('codebar workshop')
     end
+
+    it 'logs one row per member even if the delivery is performed twice' do
+      expect do
+        described_class.with(member: member).chaser.deliver_now
+        described_class.with(member:).chaser.deliver_now
+      end.to change(MemberEmailDelivery, :count).by(1)
+    end
   end
 end

spec/services/three_month_email_service_spec.rb

@@ -34,6 +34,20 @@
       member
     end
 
+    let!(:student_with_other_email_logged) do
+      member = Fabricate(:member)
+      Fabricate(:subscription, member:, group: students_group)
+      Fabricate(
+        :workshop_invitation,
+        member: member,
+        workshop: Fabricate(:workshop, chapter:, date_and_time: 6.months.ago),
+        role: 'Student',
+        attended: true
+      )
+      Fabricate(:member_email_delivery, member:, email_type: 'welcome_email')
+      member
+    end
+
     let!(:student_with_recent_attendance) do
       member = Fabricate(:member)
       Fabricate(:subscription, member: member, group: students_group)
@@ -92,17 +106,24 @@
     end
 
     it 'emails only students who have not attended in the last 3 months and were not emailed before' do
-      expect { perform_enqueued_jobs { call } }.to change(MemberEmailDelivery, :count).by(2)
+      expect { perform_enqueued_jobs { call } }.to change(MemberEmailDelivery, :count).by(3)
 
       expect(MemberEmailDelivery.where(member: eligible_student)).to exist
       expect(MemberEmailDelivery.where(member: student_with_old_attendance)).to exist
+      expect(MemberEmailDelivery.where(member: student_with_other_email_logged, email_type: 'chaser')).to exist
     end
 
     it 'does not email a member already present in member_email_deliveries' do
       expect { perform_enqueued_jobs { call } }
         .not_to(change { MemberEmailDelivery.where(member: already_emailed_student).count })
     end
 
+    it 'emails a member whose only logged delivery is of another type' do
+      expect { perform_enqueued_jobs { call } }
+        .to change { MemberEmailDelivery.where(member: student_with_other_email_logged, email_type: 'chaser').count }
+        .by(1)
+    end
+
     it 'does not email students with a recent attended workshop' do
       expect { perform_enqueued_jobs { call } }
         .not_to(change { MemberEmailDelivery.where(member: student_with_recent_attendance).count })
@@ -185,6 +206,13 @@
         role: 'Student',
         attended: true
       )
+      Fabricate(
+        :workshop_invitation,
+        member: student_with_other_email_logged,
+        workshop: Fabricate(:workshop, chapter:, date_and_time: 1.month.ago),
+        role: 'Student',
+        attended: true
+      )
 
       expect { perform_enqueued_jobs { call } }.not_to change(MemberEmailDelivery, :count)
     end