use correct txid function

returns a 32-bit integer that matches the txid assigned to electric
changes

Author: magnetised

lib/phoenix/sync/writer.ex

@@ -1413,7 +1413,7 @@ if Code.ensure_loaded?(Ecto) do
     end
 
     @txid_name {:__phoenix_sync__, :txid}
-    @txid_query "SELECT txid_current()::text as txid"
+    @txid_query "SELECT pg_current_xact_id()::xid as txid"
 
     defp start_multi do
       Ecto.Multi.new()

test/phoenix/sync/writer_test.exs

@@ -135,7 +135,7 @@ defmodule Phoenix.Sync.WriterTest do
   end
 
   defp is_txid(txid) do
-    is_binary(txid) && match?({_, ""}, Integer.parse(txid))
+    is_integer(txid)
   end
 
   # new creates without applying (so doesn't need a repo)