Calculate indexed ratio in SQL

By calculating the indexed ratio in SQL, we only have 1 round trip to
the database instead of 1 to get the max and 1 to get the min.

apps/block_scout_web/lib/block_scout_web/counters/blocks_indexed_counter.ex

@@ -39,10 +39,9 @@ defmodule BlockScoutWeb.Counters.BlocksIndexedCounter do
     ratio = Chain.indexed_ratio()
 
     finished? =
-      if ratio < 1 do
-        false
-      else
-        Chain.finished_indexing?()
+      case Decimal.cmp(ratio, 1) do
+        :lt -> false
+        _ -> Chain.finished_indexing?()
       end
 
     Notifier.broadcast_blocks_indexed_ratio(ratio, finished?)

apps/block_scout_web/test/block_scout_web/features/viewing_app_test.exs

@@ -20,7 +20,7 @@ defmodule BlockScoutWeb.ViewingAppTest do
         insert(:block, number: index)
       end
 
-      assert Explorer.Chain.indexed_ratio() == 0.5
+      assert Decimal.cmp(Explorer.Chain.indexed_ratio(), Decimal.from_float(0.5)) == :eq
 
       session
       |> AppPage.visit_page()
@@ -32,7 +32,7 @@ defmodule BlockScoutWeb.ViewingAppTest do
         insert(:block, number: index)
       end
 
-      assert Explorer.Chain.indexed_ratio() == 1.0
+      assert Decimal.cmp(Explorer.Chain.indexed_ratio(), 1) == :eq
 
       session
       |> AppPage.visit_page()
@@ -46,7 +46,7 @@ defmodule BlockScoutWeb.ViewingAppTest do
 
       BlocksIndexedCounter.calculate_blocks_indexed()
 
-      assert Explorer.Chain.indexed_ratio() == 0.5
+      assert Decimal.cmp(Explorer.Chain.indexed_ratio(), Decimal.from_float(0.5)) == :eq
 
       session
       |> AppPage.visit_page()
@@ -66,7 +66,7 @@ defmodule BlockScoutWeb.ViewingAppTest do
 
       BlocksIndexedCounter.calculate_blocks_indexed()
 
-      assert Explorer.Chain.indexed_ratio() == 0.9
+      assert Decimal.cmp(Explorer.Chain.indexed_ratio(), Decimal.from_float(0.9)) == :eq
 
       session
       |> AppPage.visit_page()
@@ -87,7 +87,7 @@ defmodule BlockScoutWeb.ViewingAppTest do
 
       BlocksIndexedCounter.calculate_blocks_indexed()
 
-      assert Explorer.Chain.indexed_ratio() == 1.0
+      assert Decimal.cmp(Explorer.Chain.indexed_ratio(), 1) == :eq
 
       session
       |> AppPage.visit_page()

apps/explorer/lib/explorer/chain.ex

@@ -835,23 +835,31 @@ defmodule Explorer.Chain do
       ...>   insert(:block, number: index)
       ...> end
       iex> Explorer.Chain.indexed_ratio()
-      0.5
+      Decimal.new(1, 50000000000000000000, -20)
 
   If there are no blocks, the percentage is 0.
 
       iex> Explorer.Chain.indexed_ratio()
-      0
+      Decimal.new(0)
 
   """
-  @spec indexed_ratio() :: float()
+  @spec indexed_ratio() :: Decimal.t()
   def indexed_ratio do
-    with {:ok, min_block_number} <- consensus_block_number(:min),
-         {:ok, max_block_number} <- consensus_block_number(:max) do
-      indexed_blocks = max_block_number - min_block_number + 1
-      indexed_blocks / (max_block_number + 1)
-    else
-      {:error, _} -> 0
-    end
+    # subquery so we need to cast less
+    decimal_min_max_query =
+      from(block in Block,
+        select: %{min_number: type(min(block.number), :decimal), max_number: type(max(block.number), :decimal)},
+        where: block.consensus == true
+      )
+
+    query =
+      from(decimal_min_max in subquery(decimal_min_max_query),
+        # math on `NULL` returns `NULL` so `coalesce` works as expected
+        select:
+          coalesce((decimal_min_max.max_number - decimal_min_max.min_number + 1) / (decimal_min_max.max_number + 1), 0)
+      )
+
+    Repo.one!(query)
   end
 
   @doc """

apps/explorer/test/explorer/chain_test.exs

@@ -921,11 +921,11 @@ defmodule Explorer.ChainTest do
         insert(:block, number: index)
       end
 
-      assert 0.5 == Chain.indexed_ratio()
+      assert Decimal.cmp(Chain.indexed_ratio(), Decimal.from_float(0.5)) == :eq
     end
 
     test "returns 0 if no blocks" do
-      assert 0 == Chain.indexed_ratio()
+      assert Decimal.new(0) == Chain.indexed_ratio()
     end
 
     test "returns 1.0 if fully indexed blocks" do
@@ -933,7 +933,7 @@ defmodule Explorer.ChainTest do
         insert(:block, number: index)
       end
 
-      assert 1.0 == Chain.indexed_ratio()
+      assert Decimal.cmp(Chain.indexed_ratio(), 1) == :eq
     end
   end