Merge pull request #1341 from poanetwork/ab-do-not-fetch-simple-token-transfers-internal-transactions

do not index internal transactions with simple token transfers

apps/explorer/lib/explorer/chain/token_transfer.ex

@@ -65,6 +65,8 @@ defmodule Explorer.Chain.TokenTransfer do
 
   @constant "0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef"
 
+  @transfer_function_signature "0xa9059cbb"
+
   @primary_key false
   schema "token_transfers" do
     field(:amount, :decimal)
@@ -115,6 +117,11 @@ defmodule Explorer.Chain.TokenTransfer do
   """
   def constant, do: @constant
 
+  @doc """
+  ERC 20's transfer(address,uint256) function signature
+  """
+  def transfer_function_signature, do: @transfer_function_signature
+
   @spec fetch_token_transfers_from_token_hash(Hash.t(), [paging_options]) :: []
   def fetch_token_transfers_from_token_hash(token_address_hash, options) do
     paging_options = Keyword.get(options, :paging_options, @default_paging_options)

apps/indexer/lib/indexer/block/realtime/fetcher.ex

@@ -12,9 +12,11 @@ defmodule Indexer.Block.Realtime.Fetcher do
   import EthereumJSONRPC, only: [integer_to_quantity: 1, quantity_to_integer: 1]
   import Indexer.Block.Fetcher, only: [async_import_tokens: 1, async_import_uncles: 1, fetch_and_import_range: 2]
 
+  alias ABI.TypeDecoder
   alias Ecto.Changeset
   alias EthereumJSONRPC.{FetchedBalances, Subscription}
   alias Explorer.Chain
+  alias Explorer.Chain.TokenTransfer
   alias Explorer.Counters.AverageBlockTime
   alias Indexer.{AddressExtraction, Block, TokenBalances, Tracer}
   alias Indexer.Block.Realtime.{ConsensusEnsurer, TaskSupervisor}
@@ -387,6 +389,31 @@ defmodule Indexer.Block.Realtime.Fetcher do
     end
   end
 
+  # 0xa9059cbb - signature of the transfer(address,uint256) function from the ERC-20 token specification.
+  # Although transaction input data can be faked we use this heuristics to filter simple token transfer internal transactions from indexing because they slow down realtime fetcher
+  defp fetch_internal_transactions?(
+         %{
+           status: :ok,
+           created_contract_address_hash: nil,
+           input: unquote(TokenTransfer.transfer_function_signature()) <> params,
+           value: 0
+         },
+         _
+       ) do
+    types = [:address, {:uint, 256}]
+
+    try do
+      [_address, _value] =
+        params
+        |> Base.decode16!(case: :mixed)
+        |> TypeDecoder.decode_raw(types)
+
+      false
+    rescue
+      _ -> true
+    end
+  end
+
   # Input-less transactions are value-transfers only, so their internal transactions do not need to be indexed
   defp fetch_internal_transactions?(%{status: :ok, created_contract_address_hash: nil, input: "0x"}, _), do: false
   # Token transfers not transferred during contract creation don't need internal transactions as the token transfers