Speed up index page queries

lib/explorer_web/controllers/block_controller.ex

@@ -1,16 +1,18 @@
 defmodule ExplorerWeb.BlockController do
-  use ExplorerWeb, :controller
-  import Ecto.Query
   alias Explorer.Block
-  alias Explorer.Repo
   alias Explorer.BlockForm
+  alias Explorer.Repo
+
+  import Ecto.Query
+
+  use ExplorerWeb, :controller
 
   def index(conn, params) do
-    blocks = Block
-      |> order_by(desc: :number)
-      |> preload(:transactions)
-      |> Repo.paginate(params)
-    render(conn, "index.html", blocks: blocks)
+    blocks = from b in Block,
+      order_by: [desc: b.number],
+      preload: :transactions
+
+    render(conn, "index.html", blocks: Repo.paginate(blocks, params))
   end
 
   def show(conn, params) do

lib/explorer_web/controllers/chain_controller.ex

@@ -2,8 +2,6 @@ defmodule ExplorerWeb.ChainController do
   alias Explorer.Block
   alias Explorer.Transaction
   alias Explorer.Repo
-  alias Explorer.BlockForm
-  alias Explorer.TransactionForm
 
   import Ecto.Query
 

lib/explorer_web/controllers/transaction_controller.ex

@@ -1,16 +1,20 @@
 defmodule ExplorerWeb.TransactionController do
-  use ExplorerWeb, :controller
-  import Ecto.Query
-  alias Explorer.Transaction
+  alias Explorer.Block
   alias Explorer.Repo
+  alias Explorer.Transaction
   alias Explorer.TransactionForm
 
+  import Ecto.Query
+
+  use ExplorerWeb, :controller
+
   def index(conn, params) do
-    transactions = Transaction
-      |> order_by(desc: :inserted_at)
-      |> preload(:block)
-      |> Repo.paginate(params)
-    render(conn, "index.html", transactions: transactions)
+    transactions = from t in Transaction,
+      join: b in Block, on: b.id == t.block_id,
+      order_by: [desc: b.number],
+      preload: :block
+
+    render(conn, "index.html", transactions: Repo.paginate(transactions, params))
   end
 
   def show(conn, params) do

test/explorer_web/controllers/transaction_controller_test.exs

@@ -13,7 +13,7 @@ defmodule ExplorerWeb.TransactionControllerTest do
     test "returns all blocks", %{conn: conn} do
       transaction_ids = insert_list(4, :transaction) |> Enum.map(fn (transaction) -> transaction.id end)
       conn = get(conn, "/en/transactions")
-      assert conn.assigns.transactions |> Enum.map(fn (transaction) -> transaction.id end) == transaction_ids
+      assert conn.assigns.transactions |> Enum.reverse |> Enum.map(fn (transaction) -> transaction.id end) == transaction_ids
     end
   end
 end