fix: merge on duplicate encounters

app/models/concerns/mergeable.rb

@@ -75,11 +75,34 @@ def invalid_record(new_record)
 
     def create_new_record(attributes)
       logger.debug "#{self} with id #{attributes["id"]} is new, creating."
-      increment_metric(:new)
 
       record = create(attributes)
+      increment_metric(:new)
       record.merge_status = :new
       record
+    rescue ActiveRecord::RecordNotUnique
+      existing_record = with_discarded.find_by(id: attributes["id"])
+      raise unless existing_record
+
+      logger.debug "#{self} with id #{attributes["id"]} was created concurrently, merging instead."
+      merge_concurrent_record(existing_record, attributes)
+    end
+
+    def merge_concurrent_record(existing_record, attributes)
+      new_record = new(attributes)
+
+      case merge_status(new_record, existing_record)
+      when :discarded
+        discarded_record(existing_record)
+      when :updated
+        update_existing_record(existing_record, attributes)
+      when :identical
+        return_identical_record(existing_record)
+      when :old
+        return_old_record(existing_record)
+      else
+        raise ActiveRecord::RecordNotUnique
+      end
     end
 
     def update_existing_record(existing_record, attributes)

spec/models/concerns/mergeable_spec.rb

@@ -83,6 +83,35 @@
     Patient.merge(updated_patient.attributes)
   end
 
+  it "merges an existing record when create races with a concurrent insert" do
+    facility = create(:facility)
+    patient = create(:patient, registration_facility: facility)
+    encountered_on = Date.new(2019, 1, 1)
+    encounter_id = Encounter.generate_id(facility.id, patient.id, encountered_on)
+    existing_encounter = create(:encounter,
+      id: encounter_id,
+      facility: facility,
+      patient: patient,
+      encountered_on: encountered_on)
+    newer_attributes = existing_encounter.attributes.merge(
+      "device_updated_at" => existing_encounter.device_updated_at + 1.hour
+    )
+
+    allow(Encounter).to receive(:create).and_raise(
+      ActiveRecord::RecordNotUnique.new(
+        'duplicate key value violates unique constraint "encounters_pkey"'
+      )
+    )
+
+    result = Encounter.merge(newer_attributes)
+
+    expect(result.id).to eq(encounter_id)
+    expect(result.merge_status).to eq(:updated)
+    expect(Encounter.count).to eq(1)
+    expect(existing_encounter.reload.device_updated_at.to_i)
+      .to eq(newer_attributes["device_updated_at"].to_i)
+  end
+
   it "works for all models" do
     new_address = FactoryBot.build(:address)
     Address.merge(new_address.attributes)