Add index

apps/explorer/priv/repo/migrations/20200521170002_create_token_transfers_token_contract_address_hash_token_id_block_number_index.exs

@@ -0,0 +1,7 @@
+defmodule Explorer.Repo.Migrations.CreateTokenTransfersTokenContractAddressHashTokenIdBlockNumberIndex do
+  use Ecto.Migration
+
+  def change do
+    create_if_not_exists(index(:token_transfers, [:token_contract_address_hash, :token_id, :block_number]))
+  end
+end