Remove duplicate blocks from changes_list before import

CHANGELOG.md

@@ -18,6 +18,7 @@
 - [#2470](https://github.com/poanetwork/blockscout/pull/2470) - Allow Realtime Fetcher to wait for small skips
 
 ### Fixes
+- [#2777](https://github.com/poanetwork/blockscout/pull/2777) - Remove duplicate blocks from changes_list before import
 - [#2755](https://github.com/poanetwork/blockscout/pull/2755) - various token instance fetcher fixes
 - [#2770](https://github.com/poanetwork/blockscout/pull/2770) - do not re-fetch token instances without uris
 - [#2761](https://github.com/poanetwork/blockscout/pull/2761) - add indexes for token instances fetching queries

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

@@ -224,7 +224,10 @@ defmodule Explorer.Chain.Import.Runner.Blocks do
     on_conflict = Map.get_lazy(options, :on_conflict, &default_on_conflict/0)
 
     # Enforce Block ShareLocks order (see docs: sharelocks.md)
-    ordered_changes_list = Enum.sort_by(changes_list, & &1.hash)
+    ordered_changes_list =
+      changes_list
+      |> Enum.sort_by(& &1.hash)
+      |> Enum.dedup_by(& &1.hash)
 
     Import.insert_changes_list(
       repo,

apps/explorer/test/explorer/chain/import/runner/blocks_test.exs

@@ -382,6 +382,20 @@ defmodule Explorer.Chain.Import.Runner.BlocksTest do
       insert_transaction(transaction2, options)
       assert Chain.missing_block_number_ranges(range) == [(block_number + 1)..(block_number + 1)]
     end
+
+    test "removes duplicate blocks (by hash) before inserting",
+         %{consensus_block: %{number: block_number, hash: block_hash, miner_hash: miner_hash}, options: options} do
+      new_block = params_for(:block, miner_hash: miner_hash, consensus: true)
+
+      %Ecto.Changeset{valid?: true, changes: block_changes} = Block.changeset(%Block{}, new_block)
+
+      result =
+        Multi.new()
+        |> Blocks.run([block_changes, block_changes], options)
+        |> Repo.transaction()
+
+      assert {:ok, %{blocks: [%{hash: block_hash, consensus: true}]}} = result
+    end
   end
 
   defp insert_block(block_params, options) do