fix: back to at least part-parallism, except sqlite

lib/bds/rebuild.ex

@@ -0,0 +1,16 @@
+defmodule BDS.Rebuild do
+  @moduledoc false
+
+  def parallel_map(items, mapper, opts \\ []) when is_list(items) and is_function(mapper, 1) do
+    max_concurrency = Keyword.get(opts, :max_concurrency, System.schedulers_online())
+    ordered = Keyword.get(opts, :ordered, true)
+    timeout = Keyword.get(opts, :timeout, :infinity)
+
+    items
+    |> Task.async_stream(mapper, max_concurrency: max_concurrency, ordered: ordered, timeout: timeout)
+    |> Enum.map(fn
+      {:ok, item} -> item
+      {:exit, reason} -> exit(reason)
+    end)
+  end
+end