Cache register status in database (#3275)

This introduces a new model, `PatientSession::RegistrationStatus`, which
stores the vaccination status of a patient-session date pair in the
database so it can queried and rendered quickly. Locally, I'm seeing the
register outcomes page on programmes with 50,000 patients load almost
instantly even when filtering on statuses. The session overview page has
a slight improvement, but that will only load quickly once the other
statuses are cached.

I've decided not to implement a state machine as had been previously
discussed, but this could be built on top of this change to enhancement
the functionality. For now, this effectively caches the existing logic
that runs on the fly to the database.

I've also decided not to implement this using Rails callbacks and
instead be explicit where the status is refreshed. This allows us to
optimise for bulk refreshes, as is necessary when adding new programmes
to sessions, running the seeds, or generally updating the status of an
entire session.

This follows up from
#3273 which
applies the same to the session status.

Author: thomasleese

app/components/app_outcome_banner_component.rb

@@ -62,7 +62,7 @@ def triage
   end
 
   def session_attendance
-    @session_attendance ||= patient_session.register_outcome.latest
+    @session_attendance ||= patient_session.todays_attendance
   end
 
   def show_location?

app/components/app_patient_session_search_result_card_component.rb

@@ -31,7 +31,7 @@ class AppPatientSessionSearchResultCardComponent < ViewComponent::Base
             end
           end %>
       
-      <% if context == :register && helpers.policy(patient_session.register_outcome.latest).new? %>
+      <% if context == :register && can_register_attendance? %>
         <div class="app-button-group">
           <%= helpers.govuk_button_to "Attending", create_session_register_path(session, patient, "present", search_form: params[:search_form]&.permit!), class: "app-button--secondary app-button--small" %>
           <%= helpers.govuk_button_to "Absent", create_session_register_path(session, patient, "absent", search_form: params[:search_form]&.permit!), class: "app-button--secondary-warning app-button--small" %>
@@ -43,20 +43,30 @@ class AppPatientSessionSearchResultCardComponent < ViewComponent::Base
   def initialize(patient_session, context:)
     super
 
-    @patient_session = patient_session
-    @patient = patient_session.patient
-    @session = patient_session.session
-    @context = context
-
     unless context.in?(%i[consent triage register record outcome])
       raise "Unknown context: #{context}"
     end
+
+    @patient_session = patient_session
+    @context = context
+
+    @patient = patient_session.patient
+    @session = patient_session.session
   end
 
   private
 
   attr_reader :patient_session, :patient, :session, :context
 
+  def can_register_attendance?
+    session_attendance =
+      SessionAttendance.new(
+        patient_session:,
+        session_date: SessionDate.new(value: Date.current)
+      )
+    helpers.policy(session_attendance).new?
+  end
+
   def link_to
     programme = patient_session.programmes.first
     session_patient_programme_path(
@@ -86,7 +96,7 @@ def status_tag
     case context
     when :register
       render AppRegisterStatusTagComponent.new(
-               patient_session.register_outcome.status
+               patient_session.registration_status&.status || "unknown"
              )
     when :consent
       statuses =

app/components/app_session_actions_component.rb

@@ -83,19 +83,14 @@ def triage_required_row
   end
 
   def register_attendance_row
-    return nil unless session.today?
+    status = "unknown"
 
-    count = patient_sessions.count { it.register_outcome.unknown? }
+    count = patient_sessions.has_registration_status(status).count
 
     return nil if count.zero?
 
     href =
-      session_register_path(
-        session,
-        search_form: {
-          register_status: PatientSession::RegisterOutcome::UNKNOWN
-        }
-      )
+      session_register_path(session, search_form: { register_status: status })
 
     {
       key: {
@@ -113,7 +108,13 @@ def ready_for_vaccinator_row
 
     counts_by_programme =
       session.programmes.index_with do |programme|
-        patient_sessions.count { it.ready_for_vaccinator?(programme:) }
+        patient_sessions
+          .has_registration_status(%w[attending completed])
+          .count do |patient_session|
+            patient_session.patient.consent_given_and_safe_to_vaccinate?(
+              programme:
+            )
+          end
       end
 
     return nil if counts_by_programme.values.all?(&:zero?)

app/components/app_vaccinate_form_component.rb

@@ -12,8 +12,8 @@ def initialize(patient_session:, programme:, vaccinate_form:)
   def render?
     patient.consent_given_and_safe_to_vaccinate?(programme:) &&
       (
-        patient_session.register_outcome.attending? ||
-          patient_session.register_outcome.completed?
+        patient_session.registration_status&.attending? ||
+          patient_session.registration_status&.completed? || false
       )
   end
 

app/controllers/sessions/record_controller.rb

@@ -16,20 +16,24 @@ class Sessions::RecordController < ApplicationController
 
   def show
     scope =
-      @session.patient_sessions.preload_for_status.in_programmes(
-        @session.programmes
-      )
+      @session
+        .patient_sessions
+        .preload_for_status
+        .in_programmes(@session.programmes)
+        .has_registration_status(%w[attending completed])
+
+    scope = @form.apply(scope)
 
     patient_sessions =
-      @form.apply(scope) do |filtered_scope|
-        filtered_scope.select(&:ready_for_vaccinator?)
+      scope.select do |patient_session|
+        patient_session.programmes.any? do |programme|
+          patient_session.patient.consent_given_and_safe_to_vaccinate?(
+            programme:
+          )
+        end
       end
 
-    if patient_sessions.is_a?(Array)
-      @pagy, @patient_sessions = pagy_array(patient_sessions)
-    else
-      @pagy, @patient_sessions = pagy(patient_sessions)
-    end
+    @pagy, @patient_sessions = pagy_array(patient_sessions)
 
     render layout: "full"
   end
@@ -65,10 +69,7 @@ def update_batch
   private
 
   def set_session
-    @session =
-      policy_scope(Session).includes(:programmes).find_by!(
-        slug: params[:session_slug]
-      )
+    @session = policy_scope(Session).find_by!(slug: params[:session_slug])
   end
 
   def set_todays_batches

app/controllers/sessions/register_controller.rb

@@ -13,7 +13,7 @@ class Sessions::RegisterController < ApplicationController
   layout "full"
 
   def show
-    @statuses = PatientSession::RegisterOutcome::STATUSES
+    @statuses = PatientSession::RegistrationStatus.statuses.keys
 
     scope =
       @session.patient_sessions.preload_for_status.in_programmes(
@@ -22,15 +22,11 @@ def show
 
     patient_sessions = @form.apply(scope)
 
-    if patient_sessions.is_a?(Array)
-      @pagy, @patient_sessions = pagy_array(patient_sessions)
-    else
-      @pagy, @patient_sessions = pagy(patient_sessions)
-    end
+    @pagy, @patient_sessions = pagy(patient_sessions)
   end
 
   def create
-    session_attendance = authorize @patient_session.register_outcome.latest
+    session_attendance = authorize @patient_session.todays_attendance
 
     ActiveRecord::Base.transaction do
       session_attendance.update!(attending: params[:status] == "present")
@@ -54,10 +50,7 @@ def create
   private
 
   def set_session
-    @session =
-      policy_scope(Session).includes(:programmes, :session_dates).find_by!(
-        slug: params[:session_slug]
-      )
+    @session = policy_scope(Session).find_by!(slug: params[:session_slug])
   end
 
   def set_patient_session

app/forms/search_form.rb

@@ -40,10 +40,6 @@ def apply(scope, programme: nil)
 
     scope = scope.search_by_nhs_number(nil) if missing_nhs_number.present?
 
-    scope = scope.order_by_name
-
-    scope = yield(scope) if block_given?
-
     if (status = consent_status).present?
       scope = scope.has_consent_status(status, programme:)
     end
@@ -57,13 +53,13 @@ def apply(scope, programme: nil)
     end
 
     if (status = register_status&.to_sym).present?
-      scope = scope.select { it.register_outcome.status == status }
+      scope = scope.has_registration_status(status)
     end
 
     if (status = triage_status&.to_sym).present?
       scope = scope.has_triage_status(status, programme:)
     end
 
-    scope
+    scope.order_by_name
   end
 end

app/lib/status_updater.rb

@@ -12,6 +12,7 @@ def initialize(patient: nil, session: nil)
 
   def call
     update_consent_statuses!
+    update_registration_statuses!
     update_session_statuses!
     update_triage_statuses!
     update_vaccination_statuses!
@@ -48,6 +49,34 @@ def update_consent_statuses!
       end
   end
 
+  def update_registration_statuses!
+    PatientSession::RegistrationStatus.import!(
+      %i[patient_session_id],
+      registration_statuses_to_import,
+      on_duplicate_key_ignore: true
+    )
+
+    PatientSession::RegistrationStatus
+      .where(patient_session_id: patient_sessions.select(:id))
+      .includes(
+        :patient,
+        :session_attendance,
+        :vaccination_records,
+        session: :programmes
+      )
+      .find_in_batches(batch_size: 10_000) do |batch|
+        batch.each(&:assign_status)
+
+        PatientSession::RegistrationStatus.import!(
+          batch.select(&:changed?),
+          on_duplicate_key_update: {
+            conflict_target: [:id],
+            columns: %i[status]
+          }
+        )
+      end
+  end
+
   def update_session_statuses!
     PatientSession::SessionStatus.import!(
       %i[patient_session_id programme_id],
@@ -142,6 +171,18 @@ def patient_session_statuses_to_import
         end
   end
 
+  def registration_statuses_to_import
+    @registration_statuses_to_import ||=
+      patient_sessions
+        .joins(:patient)
+        .pluck(:id, :"patients.birth_academic_year")
+        .filter_map do |patient_session_id, birth_academic_year|
+          if programme_ids_per_birth_academic_year.key?(birth_academic_year)
+            [patient_session_id]
+          end
+        end
+  end
+
   def programme_ids_per_birth_academic_year
     @programme_ids_per_birth_academic_year ||=
       Programme

app/models/patient_session.rb

@@ -34,6 +34,7 @@ class PatientSession < ApplicationRecord
   has_many :gillick_assessments, -> { order(:created_at) }
   has_many :pre_screenings, -> { order(:created_at) }
   has_many :session_statuses
+  has_one :registration_status
 
   has_one :location, through: :session
   has_one :team, through: :session
@@ -69,7 +70,7 @@ class PatientSession < ApplicationRecord
   scope :preload_for_status,
         -> do
           eager_load(:patient).preload(
-            :session_attendances,
+            :registration_status,
             :session_statuses,
             patient: %i[consent_statuses triage_statuses vaccination_statuses],
             session: :programmes
@@ -116,6 +117,17 @@ class PatientSession < ApplicationRecord
           )
         end
 
+  scope :has_registration_status,
+        ->(status) do
+          where(
+            PatientSession::RegistrationStatus
+              .where("patient_session_id = patient_sessions.id")
+              .where(status:)
+              .arel
+              .exists
+          )
+        end
+
   scope :has_session_status,
         ->(status, programme:) do
           where(
@@ -166,17 +178,11 @@ def session_status(programme:)
       session_statuses.build(programme:)
   end
 
-  def register_outcome
-    @register_outcome ||= PatientSession::RegisterOutcome.new(self)
-  end
-
-  def ready_for_vaccinator?(programme: nil)
-    return false if register_outcome.unknown? || register_outcome.not_attending?
-
-    programmes_to_check = programme ? [programme] : programmes
-
-    programmes_to_check.any? do
-      patient.consent_given_and_safe_to_vaccinate?(programme: it)
+  def todays_attendance
+    if (session_date = session.session_dates.today.first)
+      session_attendances.includes(:session_date).find_or_initialize_by(
+        session_date:
+      )
     end
   end
 
@@ -195,6 +201,11 @@ def next_activity(programme:)
   end
 
   def outstanding_programmes
+    if registration_status.nil? || registration_status.unknown? ||
+         registration_status.not_attending?
+      return []
+    end
+
     # If this patient hasn't been seen yet by a nurse for any of the programmes,
     # we don't want to show the banner.
     all_programmes_none_yet =
@@ -203,7 +214,8 @@ def outstanding_programmes
     return [] if all_programmes_none_yet
 
     programmes.select do |programme|
-      session_status(programme:).none_yet? && ready_for_vaccinator?(programme:)
+      session_status(programme:).none_yet? &&
+        patient.consent_given_and_safe_to_vaccinate?(programme:)
     end
   end
 end