[#558] Support xid8 type (#559)

Fixes [#558](#558)

This patch adds support for the `xid8` type introduced in PostgreSQL 13.

CHANGELOG.md

@@ -1,5 +1,10 @@
 # Changelog
 
+## v0.15.11-dev
+
+* Enhancements
+  * Support `xid8` type introduced in PostgreSQL 13
+
 ## v0.15.10 (2021-07-27)
 
 * Enhancements

lib/postgrex/binary_utils.ex

@@ -13,14 +13,18 @@ defmodule Postgrex.BinaryUtils do
     quote do: signed - 16
   end
 
-  defmacro uint16 do
-    quote do: unsigned - 16
+  defmacro uint64 do
+    quote do: unsigned - 64
   end
 
   defmacro uint32 do
     quote do: unsigned - 32
   end
 
+  defmacro uint16 do
+    quote do: unsigned - 16
+  end
+
   defmacro int8 do
     quote do: signed - 8
   end

lib/postgrex/extensions/xid8.ex

@@ -0,0 +1,25 @@
+defmodule Postgrex.Extensions.Xid8 do
+  @moduledoc false
+  import Postgrex.BinaryUtils, warn: false
+  use Postgrex.BinaryExtension, send: "xid8send"
+
+  @xid8_range 0..18_446_744_073_709_551_615
+
+  def encode(_) do
+    range = Macro.escape(@xid8_range)
+
+    quote location: :keep do
+      int when int in unquote(range) ->
+        <<8::int32, int::uint64>>
+
+      other ->
+        raise DBConnection.EncodeError, Postgrex.Utils.encode_msg(other, unquote(range))
+    end
+  end
+
+  def decode(_) do
+    quote location: :keep do
+      <<8::int32, int::uint64>> -> int
+    end
+  end
+end

lib/postgrex/utils.ex

@@ -38,7 +38,8 @@ defmodule Postgrex.Utils do
     Postgrex.Extensions.TSVector,
     Postgrex.Extensions.UUID,
     Postgrex.Extensions.VoidBinary,
-    Postgrex.Extensions.VoidText
+    Postgrex.Extensions.VoidText,
+    Postgrex.Extensions.Xid8
   ]
 
   @doc """

test/query_test.exs

@@ -734,6 +734,25 @@ defmodule QueryTest do
              catch_error(query("SELECT $1::int8", [-9_223_372_036_854_775_808 - 1]))
   end
 
+  @tag min_pg_version: "13.0"
+  test "decode xid8 from pg_current_xact_id", context do
+    assert [[int]] = query("SELECT pg_current_xact_id()", [])
+    assert is_integer(int)
+  end
+
+  @tag min_pg_version: "13.0"
+  test "encode enforces bounds on xid8", context do
+    # xid8's range is 0 to +18_446_744_073_709_551_615
+    assert [[0]] = query("SELECT $1::xid", [0])
+    assert [[18_446_744_073_709_551_615]] = query("SELECT $1::xid8", [18_446_744_073_709_551_615])
+
+    assert %DBConnection.EncodeError{} =
+             catch_error(query("SELECT $1::xid8", [18_446_744_073_709_551_615 + 1]))
+
+    assert %DBConnection.EncodeError{} =
+             catch_error(query("SELECT $1::xid", [0 - 1]))
+  end
+
   test "encode uuid", context do
     uuid = <<0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15>>
     assert [[^uuid]] = query("SELECT $1::uuid", [uuid])