Don't run imports for empty params

apps/explorer/lib/explorer/chain/import.ex

@@ -1194,20 +1194,39 @@ defmodule Explorer.Chain.Import do
   end
 
   defp import_options_to_changes_list_arguments_list(options) do
-    Enum.flat_map(@import_option_key_to_ecto_schema_module, fn {option_key, ecto_schema_module} ->
+    Enum.flat_map(
+      @import_option_key_to_ecto_schema_module,
+      &import_options_to_changes_list_arguments_list_flat_mapper(options, &1)
+    )
+  end
+
+  defp import_options_to_changes_list_arguments_list_flat_mapper(options, {option_key, ecto_schema_module}) do
     case Map.fetch(options, option_key) do
-        {:ok, option_value} when is_map(option_value) ->
+      {:ok, option_value} ->
+        import_option_to_changes_list_arguments_list_flat_mapper(option_value, ecto_schema_module)
+
+      :error ->
+        []
+    end
+  end
+
+  defp import_option_to_changes_list_arguments_list_flat_mapper(%{params: params} = option_value, ecto_schema_module) do
+    # Use `Enum.empty?` instead of `[_ | _]` as params are allowed to be any collection of maps
+    case Enum.empty?(params) do
+      false ->
         [
           [
-              Map.fetch!(option_value, :params),
+            params,
             [for: ecto_schema_module, with: Map.get(option_value, :with, :changeset)]
           ]
         ]
 
-        :error ->
+      # filter out empty params as early as possible, so that later stages don't need to deal with empty params
+      # leading to selecting all rows because they produce no where conditions as happened in
+      # https://github.com/poanetwork/blockscout/issues/850
+      true ->
         []
     end
-    end)
   end
 
   defp import_transaction(multi, options) when is_map(options) do

apps/explorer/test/explorer/chain/import_test.exs

@@ -1461,52 +1461,124 @@ defmodule Explorer.Chain.ImportTest do
     end
 
     test "timeouts can be overridden" do
-      assert {:ok, _} =
+      miner_hash = address_hash()
+      uncle_miner_hash = address_hash()
+      block_number = 0
+      block_hash = block_hash()
+      uncle_hash = block_hash()
+      from_address_hash = address_hash()
+      to_address_hash = address_hash()
+      transaction_hash = transaction_hash()
+      token_contract_address_hash = address_hash()
+
+      assert {:ok,
+              %{
+                addresses: _,
+                balances: _,
+                blocks: _,
+                block_second_degree_relations: _,
+                internal_transactions: _,
+                logs: _,
+                token_transfers: _,
+                tokens: _,
+                transactions: _,
+                transaction_forks: _,
+                token_balances: _
+              }} =
                Import.all(%{
                  addresses: %{
-                   params: [],
+                   params: [
+                     %{hash: miner_hash},
+                     %{hash: uncle_miner_hash},
+                     %{hash: to_address_hash},
+                     %{hash: from_address_hash},
+                     %{hash: token_contract_address_hash}
+                   ],
                    timeout: 1
                  },
                  balances: %{
-                   params: [],
+                   params: [
+                     %{address_hash: miner_hash, block_number: block_number, value: nil},
+                     %{address_hash: uncle_miner_hash, block_number: block_number, value: nil}
+                   ],
                    timeout: 1
                  },
                  blocks: %{
-                   params: [],
+                   params: [
+                     params_for(:block, hash: block_hash, consensus: true, miner_hash: miner_hash, number: block_number),
+                     params_for(:block,
+                       hash: uncle_hash,
+                       consensus: false,
+                       miner_hash: uncle_miner_hash,
+                       number: block_number
+                     )
+                   ],
                    timeout: 1
                  },
                  block_second_degree_relations: %{
-                   params: [],
+                   params: [%{nephew_hash: block_hash, uncle_hash: uncle_hash}],
                    timeout: 1
                  },
                  internal_transactions: %{
-                   params: [],
+                   params: [
+                     params_for(:internal_transaction,
+                       transaction_hash: transaction_hash,
+                       index: 0,
+                       from_address_hash: from_address_hash,
+                       to_address_hash: to_address_hash
+                     )
+                   ],
                    timeout: 1
                  },
                  logs: %{
-                   params: [],
+                   params: [params_for(:log, transaction_hash: transaction_hash, address_hash: miner_hash)],
                    timeout: 1
                  },
                  token_transfers: %{
-                   params: [],
+                   params: [
+                     params_for(:token_transfer,
+                       from_address_hash: from_address_hash,
+                       to_address_hash: to_address_hash,
+                       token_contract_address_hash: token_contract_address_hash,
+                       transaction_hash: transaction_hash
+                     )
+                   ],
                    timeout: 1
                  },
                  tokens: %{
-                   params: [],
+                   params: [params_for(:token, contract_address_hash: token_contract_address_hash)],
                    on_conflict: :replace_all,
                    timeout: 1
                  },
                  transactions: %{
-                   params: [],
+                   params: [
+                     params_for(:transaction,
+                       hash: transaction_hash,
+                       block_hash: block_hash,
+                       block_number: block_number,
+                       index: 0,
+                       from_address_hash: from_address_hash,
+                       to_address_hash: to_address_hash,
+                       gas_used: 0,
+                       cumulative_gas_used: 0
+                     )
+                   ],
                    on_conflict: :replace_all,
                    timeout: 1
                  },
                  transaction_forks: %{
-                   params: [],
+                   params: [%{uncle_hash: uncle_hash, hash: transaction_hash, index: 0}],
                    timeout: 1
                  },
                  token_balances: %{
-                   params: [],
+                   params: [
+                     params_for(
+                       :token_balance,
+                       address_hash: to_address_hash,
+                       token_contract_address_hash: token_contract_address_hash,
+                       block_number: block_number
+                     )
+                   ],
                    timeout: 1
                  }
                })
@@ -1631,15 +1703,14 @@ defmodule Explorer.Chain.ImportTest do
     end
 
     # https://github.com/poanetwork/blockscout/issues/850 regression test
-    test "derive_transaction_forks does not try to fork pending transactions when there are no blocks" do
+    test "derive_transaction_forks does not run when there are no blocks" do
       _pending_transaction = insert(:transaction)
 
-      {:ok, %{derive_transaction_forks: []}} =
-        Import.all(%{
+      assert Import.all(%{
                blocks: %{
                  params: []
                }
-        })
+             }) == {:ok, %{}}
     end
   end
 end

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

@@ -108,12 +108,12 @@ defmodule Indexer.Block.Catchup.Fetcher do
     {async_import_remaining_block_data_options, chain_import_options} =
       Map.split(options, @async_import_remaining_block_data_options)
 
-    with {:ok, results} = ok <-
+    with {:ok, imported} = ok <-
            chain_import_options
            |> put_in([:blocks, :params, Access.all(), :consensus], true)
            |> Chain.import() do
       async_import_remaining_block_data(
-        results,
+        imported,
         async_import_remaining_block_data_options
       )
 
@@ -122,39 +122,39 @@ defmodule Indexer.Block.Catchup.Fetcher do
   end
 
   defp async_import_remaining_block_data(
-         %{
-           block_second_degree_relations: block_second_degree_relations,
-           transactions: transaction_hashes,
-           addresses: address_hashes,
-           tokens: tokens,
-           token_balances: token_balances
-         },
+         imported,
          %{
            address_hash_to_fetched_balance_block_number: address_hash_to_block_number,
            transaction_hash_to_block_number: transaction_hash_to_block_number
          }
        ) do
-    address_hashes
+    imported
+    |> Map.get(:addresses, [])
     |> Enum.map(fn address_hash ->
       block_number = Map.fetch!(address_hash_to_block_number, to_string(address_hash))
       %{address_hash: address_hash, block_number: block_number}
     end)
     |> CoinBalance.Fetcher.async_fetch_balances()
 
-    transaction_hashes
+    imported
+    |> Map.get(:transactions, [])
     |> Enum.map(fn transaction_hash ->
       block_number = Map.fetch!(transaction_hash_to_block_number, to_string(transaction_hash))
       %{block_number: block_number, hash: transaction_hash}
     end)
     |> InternalTransaction.Fetcher.async_fetch(10_000)
 
-    tokens
+    imported
+    |> Map.get(:tokens, [])
     |> Enum.map(& &1.contract_address_hash)
     |> Token.Fetcher.async_fetch()
 
-    TokenBalance.Fetcher.async_fetch(token_balances)
+    imported
+    |> Map.get(:token_balances, [])
+    |> TokenBalance.Fetcher.async_fetch()
 
-    block_second_degree_relations
+    imported
+    |> Map.get(:block_second_degree_relations, [])
     |> Enum.map(& &1.uncle_hash)
     |> Block.Uncle.Fetcher.async_fetch_blocks()
   end

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

@@ -108,9 +108,9 @@ defmodule Indexer.Block.Realtime.Fetcher do
            |> put_in([Access.key(:balances, %{}), :params], balances_params)
            |> put_in([Access.key(:internal_transactions, %{}), :params], internal_transactions_params)
            |> put_in([Access.key(:token_balances), :params], token_balances),
-         {:ok, results} = ok <- Chain.import(chain_import_options) do
+         {:ok, imported} = ok <- Chain.import(chain_import_options) do
       TokenBalances.log_fetching_errors(__MODULE__, token_balances)
-      async_import_remaining_block_data(results)
+      async_import_remaining_block_data(imported)
       ok
     end
   end
@@ -200,12 +200,14 @@ defmodule Indexer.Block.Realtime.Fetcher do
     Enum.any?(changesets, &(Map.get(&1, :message) == "Unknown block number"))
   end
 
-  defp async_import_remaining_block_data(%{block_second_degree_relations: block_second_degree_relations, tokens: tokens}) do
-    tokens
+  defp async_import_remaining_block_data(imported) do
+    imported
+    |> Map.get(:tokens, [])
     |> Enum.map(& &1.contract_address_hash)
     |> Token.Fetcher.async_fetch()
 
-    block_second_degree_relations
+    imported
+    |> Map.get(:block_second_degree_relations, [])
     |> Enum.map(& &1.uncle_hash)
     |> Block.Uncle.Fetcher.async_fetch_blocks()
   end

apps/indexer/lib/indexer/internal_transaction/fetcher.ex

@@ -99,13 +99,14 @@ defmodule Indexer.InternalTransaction.Fetcher do
             {hash, block_number}
           end)
 
-        with {:ok, %{addresses: address_hashes}} <-
+        with {:ok, imported} <-
                Chain.import(%{
                  addresses: %{params: addresses_params},
                  internal_transactions: %{params: internal_transactions_params},
                  timeout: :infinity
                }) do
-          address_hashes
+          imported
+          |> Map.get(:addresses, [])
           |> Enum.map(fn address_hash ->
             block_number = Map.fetch!(address_hash_to_block_number, to_string(address_hash))
             %{address_hash: address_hash, block_number: block_number}

apps/indexer/test/indexer/block/fetcher_test.exs

@@ -213,9 +213,7 @@ defmodule Indexer.Block.FetcherTest do
           assert {:ok,
                   {%{
                      addresses: [%Address{hash: ^address_hash}],
-                     blocks: [%Chain.Block{hash: ^block_hash}],
-                     logs: [],
-                     transactions: []
+                     blocks: [%Chain.Block{hash: ^block_hash}]
                    }, :more}} = result
 
           wait_for_tasks(InternalTransaction.Fetcher)

apps/indexer/test/indexer/block/realtime/fetcher_test.exs

@@ -402,7 +402,6 @@ defmodule Indexer.Block.Realtime.FetcherTest do
                    %{index: 4, transaction_hash: transaction_hash},
                    %{index: 5, transaction_hash: transaction_hash}
                  ],
-                 logs: [],
                  transactions: [transaction_hash]
                }, :more}} = Indexer.Block.Fetcher.fetch_and_import_range(block_fetcher, 3_946_079..3_946_080)
     end