lib/membership/member.ex

@@ -266,6 +266,15 @@ defmodule Mv.Membership.Member do
       accept [:vereinfacht_contact_id]
     end
 
+    # Keyset-paginated read for the member overview. Filters and sort are
+    # composed onto the query by `MvWeb.MemberLive.Index.OverviewQuery`; this
+    # action only enables keyset pagination with a unique `id` tie-breaker so
+    # pages never skip or duplicate rows.
+    read :overview do
+      description "Keyset-paginated member overview read"
+      pagination keyset?: true, default_limit: 50, required?: false
+    end
+
     # Action to handle fuzzy search on specific fields
     read :search do
       argument :query, :string, allow_nil?: true
@@ -279,27 +288,7 @@ defmodule Mv.Membership.Member do
         threshold =
           Ash.Query.get_argument(query, :similarity_threshold) || @default_similarity_threshold
 
-        if is_binary(q) and String.trim(q) != "" do
+        apply_fuzzy_search_filter(query, q, threshold)
-          q2 = String.trim(q)
-          # Sanitize for LIKE patterns (escape % and _), limit length to 100 chars
-          q2_sanitized = sanitize_search_query(q2)
-          pat = "%" <> q2_sanitized <> "%"
-
-          # Build search filters grouped by search type for maintainability
-          # Priority: FTS > Substring > Custom Fields > Fuzzy Matching
-          # Note: FTS and fuzzy use q2 (unsanitized), LIKE-based filters use pat (sanitized)
-          fts_match = build_fts_filter(q2)
-          substring_match = build_substring_filter(q2_sanitized, pat)
-          custom_field_match = build_custom_field_filter(pat)
-          fuzzy_match = build_fuzzy_filter(q2, threshold)
-
-          query
-          |> Ash.Query.filter(
-            expr(^fts_match or ^substring_match or ^custom_field_match or ^fuzzy_match)
-          )
-        else
-          query
-        end
       end
     end
 
@@ -738,6 +727,13 @@ defmodule Mv.Membership.Member do
     end
   end
 
+  aggregates do
+    # Alphabetically-first group name, used to sort the overview by group DB-side.
+    # Mirrors the previous in-memory "first group name" sort key; members with no
+    # groups yield nil (sorted last ascending via NULLS LAST).
+    min :first_group_name, :groups, :name
+  end
+
   # Define identities for upsert operations
   identities do
     identity :unique_email, [:email]
@@ -1212,6 +1208,43 @@ defmodule Mv.Membership.Member do
     end
   end
 
+  @doc """
+  Applies the same fuzzy/full-text search filter as the `:search` action as a
+  plain filter on the given query, without switching the query's read action.
+
+  Used by the overview query builder so search composes with the `:overview`
+  keyset-paginated read action instead of replacing it.
+  """
+  @spec apply_overview_search(Ash.Query.t(), String.t() | nil) :: Ash.Query.t()
+  def apply_overview_search(query, q) do
+    apply_fuzzy_search_filter(query, q || "", @default_similarity_threshold)
+  end
+
+  # Shared by the `:search` action and `apply_overview_search/2`.
+  defp apply_fuzzy_search_filter(query, q, threshold) do
+    if is_binary(q) and String.trim(q) != "" do
+      q2 = String.trim(q)
+      # Sanitize for LIKE patterns (escape % and _), limit length to 100 chars
+      q2_sanitized = sanitize_search_query(q2)
+      pat = "%" <> q2_sanitized <> "%"
+
+      # Build search filters grouped by search type for maintainability
+      # Priority: FTS > Substring > Custom Fields > Fuzzy Matching
+      # Note: FTS and fuzzy use q2 (unsanitized), LIKE-based filters use pat (sanitized)
+      fts_match = build_fts_filter(q2)
+      substring_match = build_substring_filter(q2_sanitized, pat)
+      custom_field_match = build_custom_field_filter(pat)
+      fuzzy_match = build_fuzzy_filter(q2, threshold)
+
+      Ash.Query.filter(
+        query,
+        expr(^fts_match or ^substring_match or ^custom_field_match or ^fuzzy_match)
+      )
+    else
+      query
+    end
+  end
+
   # ============================================================================
   # Search Input Sanitization
   # ============================================================================

lib/membership/membership.ex

@@ -45,6 +45,7 @@ defmodule Mv.Membership do
     resource Mv.Membership.Member do
       define :create_member, action: :create_member
       define :list_members, action: :read
+      define :overview_members, action: :overview
       define :update_member, action: :update_member
       define :destroy_member, action: :destroy
     end

lib/mv_web/live/member_live/index/overview_query.ex

@@ -0,0 +1,261 @@
+defmodule MvWeb.MemberLive.Index.OverviewQuery do
+  @moduledoc """
+  Builds the Ash query for the member overview from the LiveView's filter/sort
+  state, so every filter and sort resolves in PostgreSQL via the `:overview`
+  keyset-paginated read action.
+
+  All previously in-memory passes (cycle status, boolean/date custom fields,
+  group sort) are expressed here as DB filters/sorts. A unique `id` tie-breaker
+  is always appended to the sort so keyset pages never skip or duplicate rows.
+
+  `build/1` returns an unread `Ash.Query`; the caller supplies `page:`/`actor:`
+  options to `Ash.read/2`.
+  """
+
+  import Ash.Expr
+
+  alias Mv.Membership.Member
+  alias MvWeb.MemberLive.Index.DateFilter
+
+  require Ash.Query
+
+  @type opts :: %{optional(atom()) => term()}
+
+  @doc """
+  Builds the `:overview` query from the given filter/sort options.
+
+  Recognised keys (all optional):
+
+    * `:search` — full-text search string
+    * `:group_filters` / `:groups` — `%{group_id => :in | :not_in}` and the valid groups
+    * `:fee_type_filters` / `:fee_types` — `%{fee_type_id => :in | :not_in}` and valid fee types
+    * `:date_filters` — built-in join/exit date filter map (see `DateFilter`)
+    * `:sort_field` / `:sort_order` — sort key and direction
+    * `:today` — reference date for cycle math (defaults to `Date.utc_today/0`)
+  """
+  @spec build(opts()) :: Ash.Query.t()
+  def build(opts \\ %{}) do
+    Member
+    |> Ash.Query.for_read(:overview)
+    |> apply_search(opts[:search])
+    |> apply_group_filters(opts[:group_filters], opts[:groups])
+    |> apply_fee_type_filters(opts[:fee_type_filters], opts[:fee_types])
+    |> apply_date_filters(opts[:date_filters])
+    |> apply_cycle_status_filter(
+      opts[:cycle_status_filter],
+      opts[:show_current_cycle],
+      today(opts)
+    )
+    |> apply_sort(opts[:sort_field], opts[:sort_order])
+  end
+
+  defp today(opts), do: opts[:today] || Date.utc_today()
+
+  # ---------------------------------------------------------------------------
+  # Search
+  # ---------------------------------------------------------------------------
+
+  defp apply_search(query, search) when is_binary(search),
+    do: Member.apply_overview_search(query, search)
+
+  defp apply_search(query, _), do: query
+
+  # ---------------------------------------------------------------------------
+  # Group filters (AND across selected groups)
+  # ---------------------------------------------------------------------------
+
+  defp apply_group_filters(query, group_filters, _groups)
+       when group_filters in [nil, %{}],
+       do: query
+
+  defp apply_group_filters(query, group_filters, groups) do
+    valid_ids = valid_id_set(groups)
+
+    Enum.reduce(group_filters, query, fn {group_id_str, value}, q ->
+      if MapSet.member?(valid_ids, group_id_str) do
+        apply_one_group_filter(q, group_id_str, value)
+      else
+        q
+      end
+    end)
+  end
+
+  defp apply_one_group_filter(query, group_id_str, :in) do
+    case Ecto.UUID.cast(group_id_str) do
+      {:ok, uuid} -> Ash.Query.filter(query, expr(exists(member_groups, group_id == ^uuid)))
+      _ -> query
+    end
+  end
+
+  defp apply_one_group_filter(query, group_id_str, :not_in) do
+    case Ecto.UUID.cast(group_id_str) do
+      {:ok, uuid} -> Ash.Query.filter(query, expr(not exists(member_groups, group_id == ^uuid)))
+      _ -> query
+    end
+  end
+
+  defp apply_one_group_filter(query, _id, _value), do: query
+
+  # ---------------------------------------------------------------------------
+  # Fee-type filters (:in OR; :not_in AND)
+  # ---------------------------------------------------------------------------
+
+  defp apply_fee_type_filters(query, fee_type_filters, _fee_types)
+       when fee_type_filters in [nil, %{}],
+       do: query
+
+  defp apply_fee_type_filters(query, fee_type_filters, fee_types) do
+    valid_ids = valid_id_set(fee_types)
+
+    {in_filters, not_in_filters} =
+      fee_type_filters
+      |> Enum.filter(fn {id_str, _} -> MapSet.member?(valid_ids, id_str) end)
+      |> Enum.split_with(fn {_, value} -> value == :in end)
+
+    in_uuids = cast_uuids(Enum.map(in_filters, fn {id_str, _} -> id_str end))
+
+    query =
+      if in_uuids == [] do
+        query
+      else
+        Ash.Query.filter(query, expr(membership_fee_type_id in ^in_uuids))
+      end
+
+    Enum.reduce(not_in_filters, query, fn {id_str, _}, q ->
+      case Ecto.UUID.cast(id_str) do
+        {:ok, uuid} ->
+          Ash.Query.filter(
+            q,
+            expr(membership_fee_type_id != ^uuid or is_nil(membership_fee_type_id))
+          )
+
+        _ ->
+          q
+      end
+    end)
+  end
+
+  # ---------------------------------------------------------------------------
+  # Cycle-status filter (paid/unpaid, current or last-completed cycle)
+  #
+  # Backed by the DB cycle-status aggregates (denormalized `cycle_end`). A member
+  # matches only when its selected-cycle status equals the requested status;
+  # members with no matching cycle (nil aggregate) are excluded — exactly as the
+  # previous in-memory classifier behaved.
+  # ---------------------------------------------------------------------------
+
+  defp apply_cycle_status_filter(query, status, _show_current, _today)
+       when status not in [:paid, :unpaid],
+       do: query
+
+  defp apply_cycle_status_filter(query, status, true = _show_current, today) do
+    # Current cycle: contains today; when several would, the one with the latest
+    # cycle_start wins. Keep members whose winning current cycle has `status`.
+    Ash.Query.filter(
+      query,
+      expr(
+        exists(
+          membership_fee_cycles,
+          cycle_start <= ^today and cycle_end >= ^today and status == ^status and
+            not exists(
+              member.membership_fee_cycles,
+              cycle_start <= ^today and cycle_end >= ^today and
+                cycle_start > parent(cycle_start)
+            )
+        )
+      )
+    )
+  end
+
+  defp apply_cycle_status_filter(query, status, _show_current, today) do
+    # Last completed cycle: most recent cycle that has ended (cycle_end < today).
+    Ash.Query.filter(
+      query,
+      expr(
+        exists(
+          membership_fee_cycles,
+          cycle_end < ^today and status == ^status and
+            not exists(
+              member.membership_fee_cycles,
+              cycle_end < ^today and cycle_start > parent(cycle_start)
+            )
+        )
+      )
+    )
+  end
+
+  # ---------------------------------------------------------------------------
+  # Built-in date filters (join/exit)
+  # ---------------------------------------------------------------------------
+
+  defp apply_date_filters(query, nil), do: query
+
+  defp apply_date_filters(query, filters) when is_map(filters),
+    do: DateFilter.apply_ash_filter(query, filters)
+
+  # ---------------------------------------------------------------------------
+  # Sort (always append the unique id tie-breaker for keyset stability)
+  # ---------------------------------------------------------------------------
+
+  defp apply_sort(query, nil, _order), do: Ash.Query.sort(query, id: :asc)
+  defp apply_sort(query, _field, nil), do: Ash.Query.sort(query, id: :asc)
+
+  defp apply_sort(query, field, order) do
+    case sort_key(field) do
+      nil -> Ash.Query.sort(query, id: :asc)
+      key -> Ash.Query.sort(query, [{key, order}, {:id, :asc}])
+    end
+  end
+
+  # Resolves a sort field (atom or string) to a DB sort key, or nil if it is a
+  # computed field handled elsewhere / not sortable.
+  defp sort_key(field) when field in [:membership_fee_type, "membership_fee_type"],
+    do: "membership_fee_type.name"
+
+  defp sort_key(field) when field in [:groups, "groups"], do: :first_group_name
+
+  defp sort_key(field) when is_atom(field) do
+    if field in member_sort_fields(), do: field, else: nil
+  end
+
+  defp sort_key(field) when is_binary(field) do
+    allowed = MapSet.new(member_sort_fields(), &Atom.to_string/1)
+    if MapSet.member?(allowed, field), do: String.to_existing_atom(field), else: nil
+  end
+
+  defp sort_key(_), do: nil
+
+  defp member_sort_fields do
+    Mv.Constants.member_fields() -- [:notes]
+  end
+
+  # ---------------------------------------------------------------------------
+  # Helpers
+  # ---------------------------------------------------------------------------
+
+  defp valid_id_set(records) when is_list(records) do
+    records
+    |> Enum.map(&to_string(&1.id))
+    |> Enum.map(&normalize_uuid/1)
+    |> Enum.reject(&is_nil/1)
+    |> MapSet.new()
+  end
+
+  defp valid_id_set(_), do: MapSet.new()
+
+  defp normalize_uuid(raw) when is_binary(raw) do
+    case Ecto.UUID.cast(String.trim(raw)) do
+      {:ok, uuid} -> to_string(uuid)
+      _ -> nil
+    end
+  end
+
+  defp normalize_uuid(_), do: nil
+
+  defp cast_uuids(id_strs) do
+    id_strs
+    |> Enum.map(&Ecto.UUID.cast/1)
+    |> Enum.filter(&match?({:ok, _}, &1))
+    |> Enum.map(fn {:ok, uuid} -> uuid end)
+  end
+end

test/mv_web/live/member_live/index/overview_query_test.exs

@@ -0,0 +1,135 @@
+defmodule MvWeb.MemberLive.Index.OverviewQueryTest do
+  @moduledoc """
+  Resource-level tests for the DB-backed overview query builder: keyset
+  pagination and the standard DB filters/sort pushed down from the LiveView.
+  """
+  use Mv.DataCase, async: false
+
+  import Mv.Fixtures,
+    only: [member_fixture_with_actor: 2, create_fee_type: 2, group_fixture: 1]
+
+  alias Mv.Membership
+  alias MvWeb.MemberLive.Index.OverviewQuery
+
+  setup do
+    %{actor: Mv.Helpers.SystemActor.get_system_actor()}
+  end
+
+  defp ids(results), do: Enum.map(results, & &1.id) |> MapSet.new()
+
+  defp read_all_pages(query, actor, limit) do
+    page = Ash.read!(query, page: [limit: limit], actor: actor)
+    collect_pages(page, [page.results])
+  end
+
+  defp collect_pages(%{more?: true} = page, acc) do
+    next = Ash.page!(page, :next)
+    collect_pages(next, [next.results | acc])
+  end
+
+  defp collect_pages(_page, acc), do: acc |> Enum.reverse() |> List.flatten()
+
+  describe "keyset pagination" do
+    test "concatenated pages cover the full set once with no duplicates", %{actor: actor} do
+      members =
+        for _ <- 1..5, do: member_fixture_with_actor(%{}, actor)
+
+      expected = ids(members)
+
+      query = OverviewQuery.build(%{sort_field: :inserted_at, sort_order: :asc})
+      all = read_all_pages(query, actor, 2)
+
+      assert ids(all) == expected
+      assert length(all) == length(Enum.uniq_by(all, & &1.id))
+    end
+  end
+
+  describe "DB filters" do
+    test "search matches name DB-side", %{actor: actor} do
+      hit = member_fixture_with_actor(%{first_name: "Zorblax", last_name: "Quux"}, actor)
+      _miss = member_fixture_with_actor(%{first_name: "Otto", last_name: "Normal"}, actor)
+
+      results =
+        OverviewQuery.build(%{search: "Zorblax"})
+        |> Ash.read!(actor: actor)
+
+      assert hit.id in Enum.map(results, & &1.id)
+      refute Enum.any?(results, &(&1.first_name == "Otto"))
+    end
+
+    test "group :in and :not_in resolve DB-side", %{actor: actor} do
+      group = group_fixture(%{name: "Board #{System.unique_integer([:positive])}"})
+      in_member = member_fixture_with_actor(%{}, actor)
+      out_member = member_fixture_with_actor(%{}, actor)
+
+      {:ok, _} =
+        Membership.create_member_group(%{member_id: in_member.id, group_id: group.id},
+          actor: actor
+        )
+
+      opts = %{group_filters: %{to_string(group.id) => :in}, groups: [group]}
+      in_ids = OverviewQuery.build(opts) |> Ash.read!(actor: actor) |> Enum.map(& &1.id)
+      assert in_member.id in in_ids
+      refute out_member.id in in_ids
+
+      not_opts = %{group_filters: %{to_string(group.id) => :not_in}, groups: [group]}
+      out_ids = OverviewQuery.build(not_opts) |> Ash.read!(actor: actor) |> Enum.map(& &1.id)
+      refute in_member.id in out_ids
+      assert out_member.id in out_ids
+    end
+
+    test "fee-type :in resolves DB-side", %{actor: actor} do
+      ft = create_fee_type(%{}, actor)
+      with_ft = member_fixture_with_actor(%{membership_fee_type_id: ft.id}, actor)
+      without_ft = member_fixture_with_actor(%{}, actor)
+
+      opts = %{fee_type_filters: %{to_string(ft.id) => :in}, fee_types: [ft]}
+      result_ids = OverviewQuery.build(opts) |> Ash.read!(actor: actor) |> Enum.map(& &1.id)
+
+      assert with_ft.id in result_ids
+      refute without_ft.id in result_ids
+    end
+  end
+
+  describe "group sort (DB aggregate)" do
+    test "sorts by first group name DB-side, members with groups before those without", %{
+      actor: actor
+    } do
+      g_a = group_fixture(%{name: "AAA #{System.unique_integer([:positive])}"})
+      g_z = group_fixture(%{name: "ZZZ #{System.unique_integer([:positive])}"})
+
+      m_a = member_fixture_with_actor(%{}, actor)
+      m_z = member_fixture_with_actor(%{}, actor)
+      m_none = member_fixture_with_actor(%{}, actor)
+
+      {:ok, _} =
+        Membership.create_member_group(%{member_id: m_a.id, group_id: g_a.id}, actor: actor)
+
+      {:ok, _} =
+        Membership.create_member_group(%{member_id: m_z.id, group_id: g_z.id}, actor: actor)
+
+      asc =
+        OverviewQuery.build(%{sort_field: :groups, sort_order: :asc})
+        |> Ash.read!(actor: actor)
+        |> Enum.map(& &1.id)
+        |> Enum.filter(&(&1 in [m_a.id, m_z.id, m_none.id]))
+
+      # group members first (AAA before ZZZ), member without groups last
+      assert asc == [m_a.id, m_z.id, m_none.id]
+    end
+  end
+
+  describe "sort" do
+    test "sort by last_name is deterministic with id tie-breaker", %{actor: actor} do
+      a = member_fixture_with_actor(%{last_name: "Same"}, actor)
+      b = member_fixture_with_actor(%{last_name: "Same"}, actor)
+
+      results =
+        OverviewQuery.build(%{sort_field: :last_name, sort_order: :asc})
+        |> Ash.read!(actor: actor)
+
+      ordered = results |> Enum.filter(&(&1.id in [a.id, b.id])) |> Enum.map(& &1.id)
+      assert ordered == Enum.sort([a.id, b.id])
+    end
+  end
+end

test/mv_web/member_live/index_cycle_status_filter_test.exs

@@ -0,0 +1,78 @@
+defmodule MvWeb.MemberLive.IndexCycleStatusFilterTest do
+  @moduledoc """
+  §1.13 — the paid/unpaid cycle-status filter, under the current or last-completed
+  cycle view, returns the same members as the previous in-memory classifier,
+  computed DB-side via the `cycle_end`-backed aggregates.
+  """
+  use Mv.DataCase, async: false
+
+  import Mv.Fixtures, only: [create_fee_type: 2, member_fixture_with_actor: 2, create_cycle: 4]
+
+  alias Mv.Membership.Member
+  alias MvWeb.MemberLive.Index.MembershipFeeStatus
+  alias MvWeb.MemberLive.Index.OverviewQuery
+
+  @today ~D[2024-07-15]
+
+  setup do
+    actor = Mv.Helpers.SystemActor.get_system_actor()
+    ft = create_fee_type(%{interval: :yearly}, actor)
+
+    # current 2024 paid, last-completed 2023 unpaid
+    paid_now = member_fixture_with_actor(%{membership_fee_type_id: ft.id}, actor)
+    create_cycle(paid_now, ft, %{cycle_start: ~D[2024-01-01], status: :paid}, actor)
+    create_cycle(paid_now, ft, %{cycle_start: ~D[2023-01-01], status: :unpaid}, actor)
+
+    # current 2024 unpaid, last-completed 2023 paid
+    unpaid_now = member_fixture_with_actor(%{membership_fee_type_id: ft.id}, actor)
+    create_cycle(unpaid_now, ft, %{cycle_start: ~D[2024-01-01], status: :unpaid}, actor)
+    create_cycle(unpaid_now, ft, %{cycle_start: ~D[2023-01-01], status: :paid}, actor)
+
+    # no cycles
+    _no_cycles = member_fixture_with_actor(%{membership_fee_type_id: ft.id}, actor)
+
+    %{actor: actor, paid_now: paid_now, unpaid_now: unpaid_now}
+  end
+
+  defp db_ids(status, show_current, actor) do
+    OverviewQuery.build(%{
+      cycle_status_filter: status,
+      show_current_cycle: show_current,
+      today: @today
+    })
+    |> Ash.read!(actor: actor)
+    |> MapSet.new(& &1.id)
+  end
+
+  defp oracle_ids(status, show_current, actor) do
+    Member
+    |> Ash.Query.load(membership_fee_cycles: [:membership_fee_type])
+    |> Ash.Query.load(:membership_fee_type)
+    |> Ash.read!(actor: actor)
+    |> Enum.filter(fn m ->
+      MembershipFeeStatus.get_cycle_status_for_member(m, show_current, @today) == status
+    end)
+    |> MapSet.new(& &1.id)
+  end
+
+  # {status, show_current, member-key expected in the result}
+  @cases [
+    {:paid, true, :paid_now},
+    {:unpaid, true, :unpaid_now},
+    {:paid, false, :unpaid_now},
+    {:unpaid, false, :paid_now}
+  ]
+
+  for {status, show_current, expected_key} <- @cases do
+    test "#{status} under #{if show_current, do: "current", else: "last"} cycle matches oracle",
+         %{actor: actor} = ctx do
+      status = unquote(status)
+      show_current = unquote(show_current)
+      expected = Map.fetch!(ctx, unquote(expected_key))
+
+      db = db_ids(status, show_current, actor)
+      assert db == oracle_ids(status, show_current, actor)
+      assert expected.id in db
+    end
+  end
+end

test/mv_web/member_live/index_keyset_property_test.exs

@@ -0,0 +1,86 @@
+defmodule MvWeb.MemberLive.IndexKeysetPropertyTest do
+  @moduledoc """
+  §2.2 — Keyset pagination completeness: concatenating every keyset page yields
+  exactly the full filtered set once each (no duplicates, no gaps) in a stable
+  total order.
+
+  §2.3 — Sort determinism with the unique `id` tie-breaker: members equal on the
+  sort key are ordered by `id`, and the result set equals the unsorted set.
+  """
+  use Mv.DataCase, async: false
+  use ExUnitProperties
+
+  import Mv.Fixtures, only: [member_fixture_with_actor: 2]
+
+  alias Mv.Membership.Member
+  alias MvWeb.MemberLive.Index.OverviewQuery
+
+  setup do
+    %{actor: Mv.Helpers.SystemActor.get_system_actor()}
+  end
+
+  defp clear_members(actor) do
+    Member |> Ash.read!(actor: actor) |> Enum.each(&Ash.destroy!(&1, actor: actor))
+  end
+
+  defp read_all_pages(query, actor, limit) do
+    page = Ash.read!(query, page: [limit: limit], actor: actor)
+    collect(page, page.results)
+  end
+
+  defp collect(%{more?: true} = page, acc) do
+    next = Ash.page!(page, :next)
+    collect(next, acc ++ next.results)
+  end
+
+  defp collect(_page, acc), do: acc
+
+  property "keyset pages cover the full set once, no dupes or gaps", %{actor: actor} do
+    check all(
+            n <- integer(1..12),
+            limit <- integer(1..5),
+            sort <- member_of([:last_name, :join_date, :inserted_at]),
+            order <- member_of([:asc, :desc]),
+            max_runs: 25
+          ) do
+      clear_members(actor)
+      # Deliberate ties on last_name so the tie-breaker is exercised.
+      members =
+        for i <- 1..n do
+          member_fixture_with_actor(%{last_name: "Tie#{rem(i, 3)}"}, actor)
+        end
+
+      expected = MapSet.new(members, & &1.id)
+
+      query = OverviewQuery.build(%{sort_field: sort, sort_order: order})
+      paged = read_all_pages(query, actor, limit)
+      paged_ids = Enum.map(paged, & &1.id)
+
+      assert MapSet.new(paged_ids) == expected
+      assert length(paged_ids) == MapSet.size(expected)
+    end
+  end
+
+  property "sort with ties is a deterministic total order broken by id", %{actor: actor} do
+    check all(
+            n <- integer(2..10),
+            order <- member_of([:asc, :desc]),
+            max_runs: 25
+          ) do
+      clear_members(actor)
+
+      members =
+        for _ <- 1..n do
+          member_fixture_with_actor(%{last_name: "Same"}, actor)
+        end
+
+      ordered =
+        OverviewQuery.build(%{sort_field: :last_name, sort_order: order})
+        |> Ash.read!(actor: actor)
+        |> Enum.map(& &1.id)
+
+      # All last_names equal -> order is fully determined by the id tie-breaker (asc).
+      assert ordered == Enum.sort(Enum.map(members, & &1.id))
+    end
+  end
+end