From c81cd8550d46ab3823cd132b1a7acafe6ebb9cd8 Mon Sep 17 00:00:00 2001
From: Zaiming Shi <zmstone@gmail.com>
Date: Thu, 6 May 2021 16:53:51 +0200
Subject: [PATCH] perf(trie): do not call ets:info/2 to check if table is empty

emqx_trie table is a ordered_set, with write_concurrency set to
true, the counter is not centrialsed, the ets:info/2 call to
check size == 0 is very expensive
---
 src/emqx_trie.erl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/emqx_trie.erl b/src/emqx_trie.erl
index e8a51b8ef..8ece333b0 100644
--- a/src/emqx_trie.erl
+++ b/src/emqx_trie.erl
@@ -122,7 +122,7 @@ match(Topic) when is_binary(Topic) ->
 
 %% @doc Is the trie empty?
 -spec(empty() -> boolean()).
-empty() -> ets:info(?TRIE, size) == 0.
+empty() -> ets:first(?TRIE) =:= '$end_of_table'.
 
 -spec lock_tables() -> ok.
 lock_tables() ->