fix: use single-block transactions to avoid duplicated deletions (#786)

Reading an already deleted key on a transaction will return the deleted
record anyway, so not chunking multiple blocks into a single transaction
will reduce the chances of it happening.

lib/ae_mdw/db/mutations/oracles_expiration_mutation.ex

@@ -27,6 +27,7 @@ defmodule AeMdw.Db.OraclesExpirationMutation do
     state
     |> Collection.stream(Model.ActiveOracleExpiration, {height, <<>>})
     |> Stream.take_while(&match?({^height, _pk}, &1))
+    |> Enum.to_list()
     |> Enum.reduce(state, fn {^height, pubkey}, state ->
       Oracle.expire_oracle(state, height, pubkey)
     end)

lib/ae_mdw/sync/server.ex

@@ -290,18 +290,10 @@ defmodule AeMdw.Sync.Server do
   defp exec_db_mutations(gens_mutations, state) do
     gens_mutations
     |> Enum.flat_map(fn {_height, blocks_mutations} -> blocks_mutations end)
-    |> Enum.chunk_every(2)
-    |> Enum.reduce(state, fn blocks_mutations_chunk, state ->
-      chunk_mutations =
-        blocks_mutations_chunk
-        |> Enum.flat_map(fn {_block_index, _block, block_mutations} -> block_mutations end)
-
-      new_state = State.commit_db(state, chunk_mutations)
-
-      Enum.each(blocks_mutations_chunk, fn {{_height, mbi} = _block_index, block,
-                                            _block_mutations} ->
-        broadcast_block(block, mbi == -1)
-      end)
+    |> Enum.reduce(state, fn {{_height, mbi}, block, block_mutations}, state ->
+      new_state = State.commit_db(state, block_mutations)
+
+      broadcast_block(block, mbi == -1)
 
       new_state
     end)