Optimize member count queries to avoid N+1 problem

Load all member counts in a single query during mount. Counts are stored in assigns
as a map and retrieved without additional queries.

lib/mv_web/live/membership_fee_type_live/index.ex

@@ -18,15 +18,20 @@ defmodule MvWeb.MembershipFeeTypeLive.Index do
 
   alias Mv.MembershipFees
   alias Mv.MembershipFees.MembershipFeeType
+  alias Mv.Membership
   alias Mv.Membership.Member
   alias MvWeb.Helpers.MembershipFeeHelpers
 
   @impl true
   def mount(_params, _session, socket) do
+    fee_types = load_membership_fee_types()
+    member_counts = load_member_counts(fee_types)
+
     {:ok,
      socket
      |> assign(:page_title, gettext("Membership Fee Types"))
-     |> assign(:membership_fee_types, load_membership_fee_types())}
+     |> assign(:membership_fee_types, fee_types)
+     |> assign(:member_counts, member_counts)}
   end
 
   @impl true
@@ -66,7 +71,7 @@ defmodule MvWeb.MembershipFeeTypeLive.Index do
         </:col>
 
         <:col :let={mft} label={gettext("Members")}>
-          <span class="badge badge-ghost">{get_member_count(mft)}</span>
+          <span class="badge badge-ghost">{get_member_count(mft, @member_counts)}</span>
         </:col>
 
         <:action :let={mft}>
@@ -82,18 +87,20 @@ defmodule MvWeb.MembershipFeeTypeLive.Index do
             data-confirm={gettext("Are you sure?")}
             class={[
               "btn btn-ghost btn-xs",
-              if(get_member_count(mft) > 0,
+              if(get_member_count(mft, @member_counts) > 0,
                 do: "text-error opacity-50 cursor-not-allowed",
                 else: "text-error"
               )
             ]}
             title={
-              if get_member_count(mft) > 0,
+              if get_member_count(mft, @member_counts) > 0,
                 do:
-                  gettext("Cannot delete - %{count} member(s) assigned", count: get_member_count(mft)),
+                  gettext("Cannot delete - %{count} member(s) assigned",
+                    count: get_member_count(mft, @member_counts)
+                  ),
                 else: gettext("Delete")
             }
-            disabled={get_member_count(mft) > 0}
+            disabled={get_member_count(mft, @member_counts) > 0}
           >
             <.icon name="hero-trash" class="size-4" />
           </button>
@@ -112,10 +119,12 @@ defmodule MvWeb.MembershipFeeTypeLive.Index do
     case Ash.destroy(fee_type, domain: MembershipFees) do
       :ok ->
         updated_types = Enum.reject(socket.assigns.membership_fee_types, &(&1.id == id))
+        updated_counts = Map.delete(socket.assigns.member_counts, id)
 
         {:noreply,
          socket
          |> assign(:membership_fee_types, updated_types)
+         |> assign(:member_counts, updated_counts)
          |> put_flash(:info, gettext("Membership fee type deleted"))}
 
       {:error, error} ->
@@ -131,12 +140,27 @@ defmodule MvWeb.MembershipFeeTypeLive.Index do
     |> Ash.read!(domain: MembershipFees)
   end
 
-  defp get_member_count(fee_type) do
+  # Loads all member counts for fee types in a single query to avoid N+1 queries
-    # Count members with this fee type
+  defp load_member_counts(fee_types) do
-    case Ash.count(Member |> Ash.Query.filter(membership_fee_type_id == ^fee_type.id)) do
+    fee_type_ids = Enum.map(fee_types, & &1.id)
-      {:ok, count} -> count
+
-      _ -> 0
+    # Load all members with membership_fee_type_id in a single query
+    members =
+      Member
+      |> Ash.Query.filter(membership_fee_type_id in ^fee_type_ids)
+      |> Ash.Query.select([:membership_fee_type_id])
+      |> Ash.read!(domain: Membership)
+
+    # Group by membership_fee_type_id and count
+    members
+    |> Enum.group_by(& &1.membership_fee_type_id)
+    |> Enum.map(fn {fee_type_id, members_list} -> {fee_type_id, length(members_list)} end)
+    |> Map.new()
   end
+
+  # Gets member count from preloaded assigns map
+  defp get_member_count(fee_type, member_counts) do
+    Map.get(member_counts, fee_type.id, 0)
   end
 
   defp format_error(%Ash.Error.Invalid{} = error) do