Merge pull request #249 from poanetwork/improve-paging-query-#200

Improve paging query #200

apps/explorer/lib/explorer/chain.ex

@@ -3,7 +3,8 @@ defmodule Explorer.Chain do
   The chain context.
   """
 
-  import Ecto.Query, only: [from: 2, join: 4, or_where: 3, order_by: 2, order_by: 3, preload: 2, where: 2, where: 3]
+  import Ecto.Query,
+    only: [from: 2, join: 4, limit: 2, or_where: 3, order_by: 2, order_by: 3, preload: 2, where: 2, where: 3]
 
   alias Ecto.{Changeset, Multi}
 
@@ -19,7 +20,7 @@ defmodule Explorer.Chain do
   }
 
   alias Explorer.Chain.Block.Reward
-  alias Explorer.Repo
+  alias Explorer.{PagingOptions, Repo}
 
   @typedoc """
   The name of an association on the `t:Ecto.Schema.t/0`
@@ -45,11 +46,11 @@ defmodule Explorer.Chain do
   """
   @type pagination :: map()
 
-  @typep after_hash_option :: {:after_hash, Hash.t()}
   @typep direction_option :: {:direction, direction}
   @typep inserted_after_option :: {:inserted_after, DateTime.t()}
   @typep necessity_by_association_option :: {:necessity_by_association, necessity_by_association}
   @typep pagination_option :: {:pagination, pagination}
+  @typep paging_options :: {:paging_options, PagingOptions.t()}
   @typep params_option :: {:params, map()}
   @typep timeout_option :: {:timeout, timeout}
   @typep timestamps :: %{inserted_at: DateTime.t(), updated_at: DateTime.t()}
@@ -1301,80 +1302,40 @@ defmodule Explorer.Chain do
   end
 
   @doc """
-  Returns the list of collated transactions that occurred recently (10).
+  Returns the paged list of collated transactions that occurred recently from newest to oldest using `block_number`
+  and `index`.
 
-      iex> 2 |> insert_list(:transaction) |> with_block()
-      iex> insert(:transaction) # unvalidated transaction
-      iex> 8 |> insert_list(:transaction) |> with_block()
-      iex> recent_collated_transactions = Explorer.Chain.recent_collated_transactions()
+      iex> newest_first_transactions = 50 |> insert_list(:transaction) |> with_block() |> Enum.reverse()
+      iex> oldest_seen = Enum.at(newest_first_transactions, 9)
+      iex> paging_options = %Explorer.PagingOptions{page_size: 10, key: {oldest_seen.block_number, oldest_seen.index}}
+      iex> recent_collated_transactions = Explorer.Chain.recent_collated_transactions(paging_options: paging_options)
       iex> length(recent_collated_transactions)
       10
-      iex> Enum.all?(recent_collated_transactions, fn %Explorer.Chain.Transaction{block_hash: block_hash} ->
-      ...>   !is_nil(block_hash)
-      ...> end)
+      iex> hd(recent_collated_transactions).hash == Enum.at(newest_first_transactions, 10).hash
       true
 
-  A `t:Explorer.Chain.Transaction.t/0` `hash` can be supplied to the `:after_hash` option, then only transactions in
-  after the transaction (with a greater index) in the same block or in a later block (with a greater number) will be
-  returned.  This can be used to generate paging for collated transaction.
-
-      iex> first_block = insert(:block, number: 1)
-      iex> first_transaction_in_first_block = :transaction |> insert() |> with_block(first_block)
-      iex> second_transaction_in_first_block = :transaction |> insert() |> with_block(first_block)
-      iex> second_block = insert(:block, number: 2)
-      iex> first_transaction_in_second_block = :transaction |> insert() |> with_block(second_block)
-      iex> after_first_transaciton_in_first_block = Explorer.Chain.recent_collated_transactions(
-      ...>   after_hash: first_transaction_in_first_block.hash
-      ...> )
-      iex> length(after_first_transaciton_in_first_block)
-      2
-      iex> after_second_transaciton_in_first_block = Explorer.Chain.recent_collated_transactions(
-      ...>   after_hash: second_transaction_in_first_block.hash
-      ...> )
-      iex> length(after_second_transaciton_in_first_block)
-      1
-      iex> after_first_transaciton_in_second_block = Explorer.Chain.recent_collated_transactions(
-      ...>   after_hash: first_transaction_in_second_block.hash
-      ...> )
-      iex> length(after_first_transaciton_in_second_block)
-      0
-
-  When there are no collated transactions, an empty list is returned.
-
-     iex> insert(:transaction)
-     iex> Explorer.Chain.recent_collated_transactions()
-     []
-
-  Using an unvalidated transaction's hash for `:after_hash` will also yield an empty list.
-
-     iex> %Explorer.Chain.Transaction{hash: hash} = insert(:transaction)
-     iex> insert(:transaction)
-     iex> Explorer.Chain.recent_collated_transactions(after_hash: hash)
-     []
-
   ## Options
 
     * `:necessity_by_association` - use to load `t:association/0` as `:required` or `:optional`.  If an association is
       `:required`, and the `t:Explorer.Chain.InternalTransaction.t/0` has no associated record for that association,
       then the `t:Explorer.Chain.InternalTransaction.t/0` will not be included in the list.
+    * `:paging_options` - a `t:Explorer.PagingOptions.t/0` used to specify the `:page_size` and
+      `:key` (a tuple of the lowest/oldest {block_number, index}) and. Results will be the transactions older than
+      the block number and index that are passed.
 
   """
-  @spec recent_collated_transactions([after_hash_option | necessity_by_association_option]) :: [
+  @spec recent_collated_transactions([paging_options | necessity_by_association_option]) :: [
           Transaction.t()
         ]
   def recent_collated_transactions(options \\ []) when is_list(options) do
     necessity_by_association = Keyword.get(options, :necessity_by_association, %{})
+    paging_options = Keyword.get(options, :paging_options, %PagingOptions{page_size: 50})
 
-    query =
-      from(
-        transaction in Transaction,
-        where: not is_nil(transaction.block_number) and not is_nil(transaction.index),
-        order_by: [desc: transaction.block_number, desc: transaction.index],
-        limit: 10
-      )
-
-    query
-    |> after_hash(options)
+    Transaction
+    |> where([transaction], not is_nil(transaction.block_number) and not is_nil(transaction.index))
+    |> page_transaction(paging_options)
+    |> limit(^paging_options.page_size)
+    |> order_by([transaction], desc: transaction.block_number, desc: transaction.index)
     |> join_associations(necessity_by_association)
     |> Repo.all()
   end
@@ -1674,25 +1635,6 @@ defmodule Explorer.Chain do
     |> Repo.paginate(pagination)
   end
 
-  defp after_hash(query, options) do
-    case Keyword.fetch(options, :after_hash) do
-      {:ok, hash} ->
-        from(
-          transaction in query,
-          inner_join: block in assoc(transaction, :block),
-          join: hash_transaction in Transaction,
-          on: hash_transaction.hash == ^hash,
-          inner_join: hash_block in assoc(hash_transaction, :block),
-          where:
-            block.number > hash_block.number or
-              (block.number == hash_block.number and transaction.index > hash_transaction.index)
-        )
-
-      :error ->
-        query
-    end
-  end
-
   @spec changes_list(params :: map, [{:for, module}]) :: {:ok, changes :: map} | {:error, [Changeset.t()]}
   defp changes_list(params, named_arguments) when is_list(named_arguments) do
     ecto_schema_module = Keyword.fetch!(named_arguments, :for)
@@ -1953,6 +1895,17 @@ defmodule Explorer.Chain do
     end)
   end
 
+  defp page_transaction(query, %PagingOptions{key: nil}), do: query
+
+  defp page_transaction(query, %PagingOptions{key: {block_number, index}}) do
+    query
+    |> where(
+      [transaction],
+      transaction.block_number < ^block_number or
+        (transaction.block_number == ^block_number and transaction.index < ^index)
+    )
+  end
+
   defp reverse_chronologically(query) do
     from(q in query, order_by: [desc: q.inserted_at, desc: q.hash])
   end

apps/explorer/lib/explorer/chain/transaction.ex

@@ -52,6 +52,11 @@ defmodule Explorer.Chain.Transaction do
   """
   @type standard_v :: 0..3
 
+  @typedoc """
+  The index of the transaction in its block.
+  """
+  @type transaction_index :: non_neg_integer()
+
   @typedoc """
   `t:standard_v/0` + `27`
 
@@ -114,7 +119,7 @@ defmodule Explorer.Chain.Transaction do
           gas_price: wei_per_gas,
           gas_used: Gas.t() | nil,
           hash: Hash.t(),
-          index: non_neg_integer() | nil,
+          index: transaction_index | nil,
           input: Data.t(),
           internal_transactions: %Ecto.Association.NotLoaded{} | [InternalTransaction.t()],
           internal_transactions_indexed_at: DateTime.t(),

apps/explorer/lib/explorer/paging_options.ex

@@ -0,0 +1,13 @@
+defmodule Explorer.PagingOptions do
+  @moduledoc """
+  Defines paging options for paging by a stable key such as a timestamp or block
+  number and index.
+  """
+
+  @type t :: %__MODULE__{key: key, page_size: page_size}
+
+  @typep key :: any()
+  @typep page_size :: non_neg_integer()
+
+  defstruct [:key, :page_size]
+end

apps/explorer/test/explorer/chain_test.exs

@@ -861,4 +861,15 @@ defmodule Explorer.ChainTest do
       assert block_reward.reward == Chain.block_reward(block)
     end
   end
+
+  describe "recent_collated_transactions/1" do
+    test "with no collated transactions it returns an empty list" do
+      assert [] == Explorer.Chain.recent_collated_transactions()
+    end
+
+    test "it excludes pending transactions" do
+      insert(:transaction)
+      assert [] == Explorer.Chain.recent_collated_transactions()
+    end
+  end
 end

apps/explorer_web/lib/explorer_web/controller.ex

@@ -15,4 +15,11 @@ defmodule ExplorerWeb.Controller do
     |> put_view(ExplorerWeb.ErrorView)
     |> render("404.html")
   end
+
+  def unprocessable_entity(conn) do
+    conn
+    |> put_status(:unprocessable_entity)
+    |> put_view(ExplorerWeb.ErrorView)
+    |> render("422.html")
+  end
 end

apps/explorer_web/lib/explorer_web/controllers/transaction_controller.ex

@@ -1,17 +1,24 @@
 defmodule ExplorerWeb.TransactionController do
   use ExplorerWeb, :controller
 
-  alias Explorer.Chain
+  alias Explorer.{Chain, PagingOptions}
 
-  def index(conn, params) do
-    with %{"last_seen_collated_hash" => last_seen_collated_hash_string} <- params,
-         {:ok, last_seen_collated_hash} <- Chain.string_to_transaction_hash(last_seen_collated_hash_string) do
-      do_index(conn, after_hash: last_seen_collated_hash)
+  @default_paging_options %PagingOptions{page_size: 50}
+
+  def index(conn, %{"block_number" => block_number_string, "index" => index_string}) do
+    with {block_number, ""} <- Integer.parse(block_number_string),
+         {index, ""} <- Integer.parse(index_string) do
+      do_index(conn, paging_options: %{@default_paging_options | key: {block_number, index}})
     else
-      _ -> do_index(conn)
+      _ ->
+        unprocessable_entity(conn)
     end
   end
 
+  def index(conn, _params) do
+    do_index(conn)
+  end
+
   def show(conn, %{"id" => id, "locale" => locale}) do
     redirect(conn, to: transaction_internal_transaction_path(conn, :index, locale, id))
   end
@@ -21,30 +28,29 @@ defmodule ExplorerWeb.TransactionController do
       Keyword.merge(
         [
           necessity_by_association: %{
-            block: :required,
-            from_address: :optional,
-            to_address: :optional
-          }
+            block: :required
+          },
+          paging_options: @default_paging_options
         ],
         options
       )
 
     transactions = Chain.recent_collated_transactions(full_options)
-    last_seen_collated_hash = last_seen_collated_hash(transactions)
     transaction_count = Chain.transaction_count()
 
     render(
       conn,
       "index.html",
-      last_seen_collated_hash: last_seen_collated_hash,
+      earliest: earliest(transactions),
       transaction_count: transaction_count,
       transactions: transactions
     )
   end
 
-  defp last_seen_collated_hash([]), do: nil
+  defp earliest([]), do: nil
 
-  defp last_seen_collated_hash(transactions) do
-    List.last(transactions).hash
+  defp earliest(transactions) do
+    last = List.last(transactions)
+    %{block_number: last.block_number, index: last.index}
   end
 end

apps/explorer_web/lib/explorer_web/templates/address/_link.html.eex

@@ -1,14 +1,14 @@
 <div class="address-link">
-<%= if @address do %>
-  <%= link to: address_path(@conn, :show, @conn.assigns.locale, @address),
+<%= if @address_hash do %>
+  <%= link to: address_path(@conn, :show, @conn.assigns.locale, @address_hash),
       "data-toggle": "tooltip",
       "data-placement": "top",
       class: "address-link__font",
-      title: @address do %>
+      title: @address_hash do %>
         <i class="address-link__type fas fa-address-card"></i>
-    <%= @address |> hash |> String.slice(0..3) %><i class="fas fa-ellipsis-v address-link__seperator"></i><%= @address |> hash |> String.slice(-4..-1) %>
+    <%= @address_hash |> hash() |> String.slice(0..3) %><i class="fas fa-ellipsis-v address-link__seperator"></i><%= @address_hash |> hash() |> String.slice(-4..-1) %>
 <% end %>
-<button class="address-link__copy-button" data-clipboard-text="<%= @address %>" aria-label="copy address">
+<button class="address-link__copy-button" data-clipboard-text="<%= @address_hash %>" aria-label="copy address">
   <i class="fa fa-copy"></i>
 </button>
 <% end %>

apps/explorer_web/lib/explorer_web/templates/address_internal_transaction/index.html.eex

@@ -96,10 +96,10 @@
                   </td>
                   <td><%= ExplorerWeb.BlockView.age(internal_transaction.transaction.block) %></td>
                   <td>
-                    <%= render ExplorerWeb.AddressView, "_link.html", conn: @conn, address: internal_transaction.from_address %>
+                    <%= render ExplorerWeb.AddressView, "_link.html", conn: @conn, address_hash: internal_transaction.from_address_hash %>
                   </td>
                   <td>
-                    <%= render ExplorerWeb.AddressView, "_link.html", conn: @conn, address: internal_transaction.to_address %>
+                    <%= render ExplorerWeb.AddressView, "_link.html", conn: @conn, address_hash: internal_transaction.to_address_hash %>
                   </td>
                   <td><%= ExplorerWeb.TransactionView.value(internal_transaction, include_label: false) %></td>
                 </tr>

apps/explorer_web/lib/explorer_web/templates/address_transaction/index.html.eex

@@ -103,11 +103,11 @@
                 </td>
                 <td><%= transaction.block.timestamp |> Timex.from_now %></td>
                 <td class="address-cell">
-                  <%= render ExplorerWeb.AddressView, "_link.html", conn: @conn, address: transaction.from_address %>
+                  <%= render ExplorerWeb.AddressView, "_link.html", conn: @conn, address_hash: transaction.from_address_hash %>
                 </td>
                 <td class="u-text-center"><i class="fas fa-arrow-circle-right"></i></td>
                 <td>
-                  <%= render ExplorerWeb.AddressView, "_link.html", conn: @conn, address: transaction.to_address %>
+                  <%= render ExplorerWeb.AddressView, "_link.html", conn: @conn, address_hash: transaction.to_address_hash %>
                 </td>
                 <td><%= ExplorerWeb.TransactionView.value(transaction, include_label: false) %></td>
                 <td><%= ExplorerWeb.TransactionView.formatted_fee(transaction, denomination: :ether) %></td>

apps/explorer_web/lib/explorer_web/templates/block_transaction/index.html.eex

@@ -164,11 +164,11 @@
                     <%= transaction.block.timestamp |> Timex.from_now %>
                   </td>
                   <td class="address-cell">
-                    <%= render ExplorerWeb.AddressView, "_link.html", conn: @conn, address: transaction.from_address %>
+                    <%= render ExplorerWeb.AddressView, "_link.html", conn: @conn, address_hash: transaction.from_address_hash %>
                   </td>
                   <td class="u-text-center"><i class="fas fa-arrow-circle-right"></i></td>
                   <td>
-                      <%= render ExplorerWeb.AddressView, "_link.html", conn: @conn, address: transaction.to_address %>
+                      <%= render ExplorerWeb.AddressView, "_link.html", conn: @conn, address_hash: transaction.to_address_hash %>
                   </td>
                   <td>
                     <%= ExplorerWeb.TransactionView.value(transaction) %>

apps/explorer_web/lib/explorer_web/templates/chain/_blocks.html.eex

@@ -21,7 +21,7 @@
           <td><%= block.transactions |> Enum.count %></td>
           <td><%= block.gas_used |> Cldr.Number.to_string! %></td>
           <td>
-            <%= render ExplorerWeb.AddressView, "_link.html", conn: @conn, address: block.miner %>
+            <%= render ExplorerWeb.AddressView, "_link.html", conn: @conn, address_hash: block.miner_hash %>
           </td>
         </tr>
         <% end %>

apps/explorer_web/lib/explorer_web/templates/chain/_transactions.html.eex

@@ -17,10 +17,10 @@
             <%= render ExplorerWeb.TransactionView, "_link.html", conn: @conn, transaction: transaction %>
           </td>
           <td>
-            <%= render ExplorerWeb.AddressView, "_link.html", conn: @conn, address: transaction.from_address %>
+            <%= render ExplorerWeb.AddressView, "_link.html", conn: @conn, address_hash: transaction.from_address_hash %>
           </td>
           <td>
-            <%= render ExplorerWeb.AddressView, "_link.html", conn: @conn, address: transaction.to_address %>
+            <%= render ExplorerWeb.AddressView, "_link.html", conn: @conn, address_hash: transaction.to_address_hash %>
           </td>
           <td><%= ExplorerWeb.TransactionView.value(transaction, include_label: false) %> </td>
           <td><%= transaction.block.timestamp |> Timex.from_now() %></td>

apps/explorer_web/lib/explorer_web/templates/pending_transaction/index.html.eex

@@ -50,10 +50,10 @@
               </td>
               <td><%= last_seen(transaction) %></td>
               <td>
-                <%= render ExplorerWeb.AddressView, "_link.html", conn: @conn, address: transaction.from_address %>
+                <%= render ExplorerWeb.AddressView, "_link.html", conn: @conn, address_hash: transaction.from_address_hash %>
               </td>
               <td>
-                <%= render ExplorerWeb.AddressView, "_link.html", conn: @conn, address: transaction.to_address %>
+                <%= render ExplorerWeb.AddressView, "_link.html", conn: @conn, address_hash: transaction.to_address_hash %>
               </td>
               <td>
               <%= ExplorerWeb.TransactionView.value(transaction, include_label: false) %>

apps/explorer_web/lib/explorer_web/templates/transaction/index.html.eex

@@ -50,19 +50,19 @@
               </td>
               <td>
                 <%= link(
-                      transaction.block,
+                      transaction.block_number,
                       class: "transactions__link",
                       to: block_path(@conn, :show, @conn.assigns.locale, transaction.block)
                     ) %>
               </td>
               <td>
-                <%= transaction.block.timestamp |> Timex.from_now %>
+                <%= transaction.block.timestamp %>
               </td>
               <td>
-                <%= render ExplorerWeb.AddressView, "_link.html", conn: @conn, address: transaction.from_address %>
+                <%= render ExplorerWeb.AddressView, "_link.html", conn: @conn, address_hash: transaction.from_address_hash %>
               </td>
               <td>
-                <%= render ExplorerWeb.AddressView, "_link.html", conn: @conn, address: transaction.to_address %>
+                <%= render ExplorerWeb.AddressView, "_link.html", conn: @conn, address_hash: transaction.to_address_hash %>
               </td>
               <td>
                 <%= ExplorerWeb.TransactionView.value(transaction, include_label: false) %>
@@ -73,16 +73,16 @@
       </table>
     </div>
   </div>
-  <%= if @last_seen_collated_hash do %>
+  <%= if @earliest do %>
     <%= link(
-          gettext("Next Page"),
-          class: "button button--secondary button--sm u-float-right mt-3",
-          to: transaction_path(
-            @conn,
-            :index,
-            @conn.assigns.locale,
-            %{"last_seen_collated_hash" => to_string(@last_seen_collated_hash)}
-          )
-        ) %>
+      gettext("Older"),
+      class: "button button--secondary button--sm u-float-right mt-3",
+      to: transaction_path(
+        @conn,
+        :index,
+        @conn.assigns.locale,
+        %{"block_number" => @earliest.block_number, "index" => @earliest.index}
+      )
+    ) %>
   <% end %>
 </section>

apps/explorer_web/lib/explorer_web/templates/transaction_internal_transaction/index.html.eex

@@ -38,10 +38,10 @@
                 <tr>
                   <td><%= internal_transaction.call_type %></td>
                   <td>
-                    <%= render ExplorerWeb.AddressView, "_link.html", conn: @conn, address: internal_transaction.from_address %>
+                    <%= render ExplorerWeb.AddressView, "_link.html", conn: @conn, address_hash: internal_transaction.from_address_hash %>
                   </td>
                   <td>
-                    <%= render ExplorerWeb.AddressView, "_link.html", conn: @conn, address: internal_transaction.to_address %>
+                    <%= render ExplorerWeb.AddressView, "_link.html", conn: @conn, address_hash: internal_transaction.to_address_hash %>
                   </td>
                   <td><%= ExplorerWeb.TransactionView.value(internal_transaction, include_label: false) %></td>
                   <td><%= ExplorerWeb.TransactionView.gas(internal_transaction) %></td>

apps/explorer_web/lib/explorer_web/views/address_view.ex

@@ -2,6 +2,7 @@ defmodule ExplorerWeb.AddressView do
   use ExplorerWeb, :view
 
   alias Explorer.Chain.{Address, Wei}
+  alias Explorer.Chain.Hash
   alias Explorer.ExchangeRates.Token
   alias ExplorerWeb.ExchangeRates.USD
 
@@ -41,7 +42,7 @@ defmodule ExplorerWeb.AddressView do
     end
   end
 
-  def hash(%Address{hash: hash}) do
+  def hash(%Hash{} = hash) do
     to_string(hash)
   end
 

apps/explorer_web/lib/explorer_web/views/error_view.ex

@@ -5,6 +5,10 @@ defmodule ExplorerWeb.ErrorView do
     "Page not found"
   end
 
+  def render("422.html", _assigns) do
+    "Unprocessable entity"
+  end
+
   def render("500.html", _assigns) do
     "Internal server error"
   end

apps/explorer_web/priv/gettext/default.pot

@@ -155,7 +155,7 @@ msgstr ""
 
 #: lib/explorer_web/templates/address/overview.html.eex:11
 #: lib/explorer_web/templates/transaction_log/index.html.eex:29
-#: lib/explorer_web/views/address_view.ex:17
+#: lib/explorer_web/views/address_view.ex:18
 msgid "Address"
 msgstr ""
 
@@ -302,7 +302,6 @@ msgid "TPM"
 msgstr ""
 
 #: lib/explorer_web/templates/pending_transaction/index.html.eex:69
-#: lib/explorer_web/templates/transaction/index.html.eex:78
 msgid "Next Page"
 msgstr ""
 
@@ -497,7 +496,7 @@ msgstr ""
 msgid "Contract"
 msgstr ""
 
-#: lib/explorer_web/views/address_view.ex:15
+#: lib/explorer_web/views/address_view.ex:16
 msgid "Contract Address"
 msgstr ""
 
@@ -508,3 +507,7 @@ msgstr ""
 #: lib/explorer_web/templates/block_transaction/index.html.eex:181
 msgid "There are no Transactions"
 msgstr ""
+
+#: lib/explorer_web/templates/transaction/index.html.eex:78
+msgid "Older"
+msgstr ""

apps/explorer_web/priv/gettext/en/LC_MESSAGES/default.po

@@ -167,7 +167,7 @@ msgstr "%{count} transactions in this block"
 
 #: lib/explorer_web/templates/address/overview.html.eex:11
 #: lib/explorer_web/templates/transaction_log/index.html.eex:29
-#: lib/explorer_web/views/address_view.ex:17
+#: lib/explorer_web/views/address_view.ex:18
 msgid "Address"
 msgstr "Address"
 
@@ -314,7 +314,6 @@ msgid "TPM"
 msgstr ""
 
 #: lib/explorer_web/templates/pending_transaction/index.html.eex:69
-#: lib/explorer_web/templates/transaction/index.html.eex:78
 msgid "Next Page"
 msgstr ""
 
@@ -509,7 +508,7 @@ msgstr ""
 msgid "Contract"
 msgstr ""
 
-#: lib/explorer_web/views/address_view.ex:15
+#: lib/explorer_web/views/address_view.ex:16
 msgid "Contract Address"
 msgstr ""
 
@@ -520,3 +519,7 @@ msgstr ""
 #: lib/explorer_web/templates/block_transaction/index.html.eex:181
 msgid "There are no Transactions"
 msgstr ""
+
+#: lib/explorer_web/templates/transaction/index.html.eex:78
+msgid "Older"
+msgstr ""

apps/explorer_web/test/explorer_web/controllers/transaction_controller_test.exs

@@ -1,10 +1,11 @@
 defmodule ExplorerWeb.TransactionControllerTest do
   use ExplorerWeb.ConnCase
+  alias Explorer.Chain.Transaction
 
   import ExplorerWeb.Router.Helpers, only: [transaction_path: 4, transaction_internal_transaction_path: 4]
 
   describe "GET index/2" do
-    test "returns a transaction with a receipt", %{conn: conn} do
+    test "returns a collated transactions", %{conn: conn} do
       transaction =
         :transaction
         |> insert()
@@ -22,43 +23,61 @@ defmodule ExplorerWeb.TransactionControllerTest do
 
       conn = get(conn, "/en/transactions")
 
-      assert length(conn.assigns.transactions) == 1
+      assert conn.assigns.transaction_count == 1
     end
 
-    test "returns no pending transactions", %{conn: conn} do
-      insert(:transaction)
-
-      conn = get(conn, "/en/transactions")
-
-      assert conn.assigns.transactions == []
-    end
+    test "excludes pending transactions", %{conn: conn} do
+      %Transaction{hash: hash} =
+        :transaction
+        |> insert()
+        |> with_block()
 
-    test "only returns transactions that have a receipt", %{conn: conn} do
       insert(:transaction)
 
       conn = get(conn, "/en/transactions")
 
-      assert length(conn.assigns.transactions) == 0
+      assert [%Transaction{hash: ^hash}] = conn.assigns.transactions
     end
 
-    test "paginates transactions using the last seen transaction", %{conn: conn} do
-      transaction =
+    test "returns next page of results based on last seen transaction", %{conn: conn} do
+      second_page_hashes =
+        50
+        |> insert_list(:transaction)
+        |> with_block()
+        |> Enum.map(& &1.hash)
+
+      %Transaction{block_number: block_number, index: index} =
         :transaction
         |> insert()
         |> with_block()
 
       conn =
-        get(
-          conn,
-          "/en/transactions",
-          last_seen_collated_hash: to_string(transaction.hash)
-        )
+        get(conn, "/en/transactions", %{
+          "block_number" => Integer.to_string(block_number),
+          "index" => Integer.to_string(index)
+        })
 
-      assert conn.assigns.transactions == []
+      actual_hashes =
+        conn.assigns.transactions
+        |> Enum.map(& &1.hash)
+        |> Enum.reverse()
+
+      assert second_page_hashes == actual_hashes
+    end
+
+    test "guards against bad block_number input", %{conn: conn} do
+      conn = get(conn, "/en/transactions", %{"block_number" => "foo", "index" => "2"})
+      assert html_response(conn, 422)
+    end
+
+    test "guards against bad index input", %{conn: conn} do
+      conn = get(conn, "/en/transactions", %{"block_number" => "2", "index" => "bar"})
+      assert html_response(conn, 422)
     end
 
     test "sends back the number of transactions", %{conn: conn} do
       insert(:transaction)
+      |> with_block()
 
       conn = get(conn, "/en/transactions")
 

apps/explorer_web/test/explorer_web/views/error_view_test.exs

@@ -8,6 +8,10 @@ defmodule ExplorerWeb.ErrorViewTest do
     assert render_to_string(ExplorerWeb.ErrorView, "404.html", []) == "Page not found"
   end
 
+  test "renders 422.html" do
+    assert render_to_string(ExplorerWeb.ErrorView, "422.html", []) == "Unprocessable entity"
+  end
+
   test "render 500.html" do
     assert render_to_string(ExplorerWeb.ErrorView, "500.html", []) == "Internal server error"
   end