Fetch rewards in parallel with transactions

Problem: the Address main page is too slow. Part of the reason is that it has to execute 3 queries.

Solution: since 2 of these queries are unrelated to each other (transactions and rewards) they will be executed in parallel.

CHANGELOG.md

@@ -1,6 +1,7 @@
 ## Current
 
 ### Features
+- [#2352](https://github.com/poanetwork/blockscout/pull/2352) - Fetch rewards in parallel with transactions
 - [#2294](https://github.com/poanetwork/blockscout/pull/2294) - add healthy block period checking endpoint
 
 ### Fixes

apps/block_scout_web/lib/block_scout_web/controllers/address_transaction_controller.ex

@@ -23,7 +23,8 @@ defmodule BlockScoutWeb.AddressTransactionController do
       [token_transfers: :token] => :optional,
       [token_transfers: :to_address] => :optional,
       [token_transfers: :from_address] => :optional,
-      [token_transfers: :token_contract_address] => :optional
+      [token_transfers: :token_contract_address] => :optional,
+      :block => :required
     }
   ]
 
@@ -34,7 +35,6 @@ defmodule BlockScoutWeb.AddressTransactionController do
          {:ok, address} <- Chain.hash_to_address(address_hash, address_options, false) do
       options =
         @transaction_necessity_by_association
-        |> put_in([:necessity_by_association, :block], :required)
         |> Keyword.merge(paging_options(params))
         |> Keyword.merge(current_filter(params))
 

apps/explorer/lib/explorer/chain.ex

@@ -222,25 +222,17 @@ defmodule Explorer.Chain do
           Transaction.t()
         ]
   def address_to_transactions_with_rewards(address_hash, options \\ []) when is_list(options) do
-    direction = Keyword.get(options, :direction)
-    necessity_by_association = Keyword.get(options, :necessity_by_association, %{})
     paging_options = Keyword.get(options, :paging_options, @default_paging_options)
 
-    transaction_hashes_from_token_transfers =
-      TokenTransfer.where_any_address_fields_match(direction, address_hash, paging_options)
-
-    transactions_list =
-      paging_options
-      |> fetch_transactions()
-      |> Transaction.where_transaction_matches(transaction_hashes_from_token_transfers, direction, address_hash)
-      |> join_associations(necessity_by_association)
-      |> Transaction.preload_token_transfers(address_hash)
-      |> Repo.all()
-
     if Application.get_env(:block_scout_web, BlockScoutWeb.Chain)[:has_emission_funds] do
+      rewards_task =
+        Task.async(fn ->
+          Reward.fetch_emission_rewards_tuples(address_hash, paging_options)
+        end)
+
       address_hash
-      |> Reward.fetch_emission_rewards_tuples(paging_options)
-      |> Enum.concat(transactions_list)
+      |> address_to_transactions_without_rewards(paging_options, options)
+      |> Enum.concat(Task.await(rewards_task))
       |> Enum.sort_by(fn item ->
         case item do
           {%Reward{} = emission_reward, _} ->
@@ -252,10 +244,25 @@ defmodule Explorer.Chain do
       end)
       |> Enum.take(paging_options.page_size)
     else
-      transactions_list
+      address_to_transactions_without_rewards(address_hash, paging_options, options)
     end
   end
 
+  defp address_to_transactions_without_rewards(address_hash, paging_options, options) do
+    direction = Keyword.get(options, :direction)
+    necessity_by_association = Keyword.get(options, :necessity_by_association, %{})
+
+    transaction_hashes_from_token_transfers =
+      TokenTransfer.where_any_address_fields_match(direction, address_hash, paging_options)
+
+    paging_options
+    |> fetch_transactions()
+    |> Transaction.where_transaction_matches(transaction_hashes_from_token_transfers, direction, address_hash)
+    |> join_associations(necessity_by_association)
+    |> Transaction.preload_token_transfers(address_hash)
+    |> Repo.all()
+  end
+
   @spec address_to_logs(Hash.Address.t(), Keyword.t()) :: [Log.t()]
   def address_to_logs(address_hash, options \\ []) when is_list(options) do
     paging_options = Keyword.get(options, :paging_options) || %PagingOptions{page_size: 50}