fix: cursor pagination on events index repeating same rows

.gitignore

@@ -35,3 +35,4 @@ docker-compose.yml
 node_modules
 .serena
 .playwright-mcp
+.claude

lib/mailgun_logger/events/event.ex

@@ -60,9 +60,9 @@ defmodule MailgunLogger.Event do
       :message_subject,
       :account_id
     ],
-    sortable: [:inserted_at, :id],
+    sortable: [:timestamp, :id],
     default_order: %{
-      order_by: [:inserted_at, :id],
+      order_by: [:timestamp, :id],
       order_directions: [:desc, :asc]
     },
     default_pagination_type: :first,

lib/mailgun_logger/events/events.ex

@@ -18,7 +18,6 @@ defmodule MailgunLogger.Events do
       )
 
     Event
-    |> order_by([e], desc: e.timestamp)
     |> select([e], ^fields)
     |> Flop.validate_and_run(params, for: Event)
   end
@@ -192,5 +191,4 @@ defmodule MailgunLogger.Events do
       %{count: count} -> count
     end
   end
-
 end

priv/repo/migrations/20260424081601_replace_events_pagination_index.exs

@@ -0,0 +1,15 @@
+defmodule MailgunLogger.Repo.Migrations.ReplaceEventsPaginationIndex do
+  use Ecto.Migration
+
+  def change do
+    execute(
+      "CREATE INDEX IF NOT EXISTS events_timestamp_id_idx ON events (timestamp DESC, id)",
+      "DROP INDEX IF EXISTS events_timestamp_id_idx"
+    )
+
+    execute(
+      "DROP INDEX IF EXISTS events_timestamp_inserted_at_id_idx",
+      "CREATE INDEX IF NOT EXISTS events_timestamp_inserted_at_id_idx ON events (timestamp DESC, inserted_at DESC, id)"
+    )
+  end
+end

test/lib/mailgun_logger/events/events_test.exs

@@ -0,0 +1,68 @@
+defmodule MailgunLogger.EventsTest do
+  use MailgunLogger.DataCase
+
+  alias MailgunLogger.Events
+
+  describe "search_events/2 cursor pagination" do
+    test "next page returns rows that are not on the previous page" do
+      account = insert(:account)
+
+      for i <- 1..30 do
+        insert(:event,
+          account: account,
+          timestamp: NaiveDateTime.add(~N[2026-01-01 00:00:00], i, :second)
+        )
+      end
+
+      {:ok, {page1, meta1}} = Events.search_events(%{"first" => 10})
+      assert length(page1) == 10
+      assert meta1.has_next_page?
+      assert is_binary(meta1.end_cursor)
+
+      {:ok, {page2, meta2}} = Events.search_events(%{"first" => 10, "after" => meta1.end_cursor})
+      assert length(page2) == 10
+
+      page1_ids = Enum.map(page1, & &1.id)
+      page2_ids = Enum.map(page2, & &1.id)
+
+      assert MapSet.disjoint?(MapSet.new(page1_ids), MapSet.new(page2_ids)),
+             "page 2 must not repeat ids from page 1, got overlap: " <>
+               inspect(MapSet.intersection(MapSet.new(page1_ids), MapSet.new(page2_ids)))
+
+      {:ok, {page3, _meta3}} = Events.search_events(%{"first" => 10, "after" => meta2.end_cursor})
+      page3_ids = Enum.map(page3, & &1.id)
+
+      assert MapSet.disjoint?(MapSet.new(page2_ids), MapSet.new(page3_ids)),
+             "page 3 must not repeat ids from page 2, got overlap: " <>
+               inspect(MapSet.intersection(MapSet.new(page2_ids), MapSet.new(page3_ids)))
+
+      assert MapSet.equal?(
+               MapSet.new(page1_ids ++ page2_ids ++ page3_ids),
+               MapSet.new(page1_ids ++ page2_ids ++ page3_ids) |> MapSet.to_list() |> MapSet.new()
+             )
+
+      assert length(page1_ids ++ page2_ids ++ page3_ids) == 30
+    end
+
+    test "rows are ordered by timestamp descending across pages" do
+      account = insert(:account)
+
+      for i <- 1..30 do
+        insert(:event,
+          account: account,
+          timestamp: NaiveDateTime.add(~N[2026-01-01 00:00:00], i, :second)
+        )
+      end
+
+      {:ok, {page1, meta1}} = Events.search_events(%{"first" => 10})
+      {:ok, {page2, _meta2}} = Events.search_events(%{"first" => 10, "after" => meta1.end_cursor})
+
+      last_of_page1 = List.last(page1).timestamp
+      first_of_page2 = List.first(page2).timestamp
+
+      assert NaiveDateTime.compare(first_of_page2, last_of_page1) in [:lt, :eq],
+             "expected page 2 to continue chronologically after page 1, " <>
+               "but page 1 ends at #{last_of_page1} and page 2 starts at #{first_of_page2}"
+    end
+  end
+end

test/support/factory.ex

@@ -2,6 +2,7 @@ defmodule MailgunLogger.Factory do
   use ExMachina.Ecto, repo: MailgunLogger.Repo
 
   alias MailgunLogger.Account
+  alias MailgunLogger.Event
   alias MailgunLogger.User
   alias MailgunLogger.Role
   alias MailgunLogger.UserRole
@@ -16,6 +17,21 @@ defmodule MailgunLogger.Factory do
     }
   end
 
+  def event_factory() do
+    %Event{
+      api_id: sequence(:api_id, &"api_id_#{&1}"),
+      event: "delivered",
+      log_level: "info",
+      method: "http",
+      recipient: sequence(:recipient, &"to_#{&1}@example.com"),
+      message_from: "from@example.com",
+      message_subject: sequence(:subject, &"subject #{&1}"),
+      message_id: sequence(:message_id, &"mid_#{&1}"),
+      timestamp: ~N[2026-01-01 00:00:00],
+      account: build(:account)
+    }
+  end
+
   def user_factory() do
     %User{
       email: sequence(:email, &"joe-#{&1}@email.com"),