faster varint encoding

bench/varint.exs

@@ -0,0 +1,38 @@
+Benchee.run(
+  %{
+    "old" => fn input -> Enum.each(input, &Ch.RowBinary.encode_varint/1) end,
+    "new" => fn input -> Enum.each(input, &Ch.RowBinary.encode_varint_new/1) end
+  },
+  inputs: %{
+    "small" => Enum.to_list(0..10000),
+    "medium" => Enum.to_list(100_000..110_000),
+    "large" => Enum.to_list(10_000_000..10_010_000)
+  }
+)
+
+# ##### With input large #####
+# Name           ips        average  deviation         median         99th %
+# new        11.16 K       89.57 μs     ±4.27%       89.04 μs      104.63 μs
+# old         4.79 K      208.97 μs     ±3.67%      207.54 μs      242.17 μs
+
+# Comparison:
+# new        11.16 K
+# old         4.79 K - 2.33x slower +119.40 μs
+
+# ##### With input medium #####
+# Name           ips        average  deviation         median         99th %
+# new        12.59 K       79.41 μs     ±4.36%       78.96 μs       93.58 μs
+# old         6.05 K      165.30 μs     ±3.81%      164.17 μs      183.21 μs
+
+# Comparison:
+# new        12.59 K
+# old         6.05 K - 2.08x slower +85.89 μs
+
+# ##### With input small #####
+# Name           ips        average  deviation         median         99th %
+# new        14.53 K       68.82 μs     ±4.09%       68.50 μs       80.67 μs
+# old         8.23 K      121.52 μs     ±3.67%      120.83 μs      135.03 μs
+
+# Comparison:
+# new        14.53 K
+# old         8.23 K - 1.77x slower +52.70 μs

lib/ch/row_binary.ex

@@ -178,6 +178,38 @@ defmodule Ch.RowBinary do
     raise ArgumentError, "unsupported type for encoding: #{inspect(type)}"
   end
 
+  @doc false
+  def encode_varint(i) when is_integer(i) and i < 128, do: i
+  def encode_varint(i) when is_integer(i), do: encode_varint_cont(i)
+
+  @doc false
+  def encode_varint_new(v) when v < 1 <<< 7, do: v
+  def encode_varint_new(v) when v < 1 <<< 14, do: <<1::1, v::7, v >>> 7>>
+  def encode_varint_new(v) when v < 1 <<< 21, do: <<1::1, v::7, 1::1, v >>> 7::7, v >>> 14>>
+
+  def encode_varint_new(v) when v < 1 <<< 28,
+    do: <<1::1, v::7, 1::1, v >>> 7::7, 1::1, v >>> 14::7, v >>> 21>>
+
+  def encode_varint_new(v) when v < 1 <<< 35,
+    do: <<1::1, v::7, 1::1, v >>> 7::7, 1::1, v >>> 14::7, 1::1, v >>> 21::7, v >>> 28>>
+
+  def encode_varint_new(v) when v < 1 <<< 42,
+    do:
+      <<1::1, v::7, 1::1, v >>> 7::7, 1::1, v >>> 14::7, 1::1, v >>> 21::7, 1::1, v >>> 28::7,
+        v >>> 35>>
+
+  def encode_varint_new(v) when v < 1 <<< 49,
+    do:
+      <<1::1, v::7, 1::1, v >>> 7::7, 1::1, v >>> 14::7, 1::1, v >>> 21::7, 1::1, v >>> 28::7,
+        1::1, v >>> 35::7, v >>> 42>>
+
+  def encode_varint_new(v) when v < 1 <<< 56,
+    do:
+      <<1::1, v::7, 1::1, v >>> 7::7, 1::1, v >>> 14::7, 1::1, v >>> 21::7, 1::1, v >>> 28::7,
+        1::1, v >>> 35::7, 1::1, v >>> 42::7, v >>> 49>>
+
+  def encode_varint_new(v), do: <<1::1, v::7, encode_varint_new(v >>> 7)::bytes>>
+
   @doc false
   def encode(type, value)