From 80ef076ceec35857bffec62d146038ceac656ece Mon Sep 17 00:00:00 2001
From: Turtle <deng@emqx.io>
Date: Sat, 8 May 2021 16:32:17 +0800
Subject: [PATCH] feat(rule_engine): rule sql add null function

---
 apps/emqx_rule_engine/src/emqx_rule_funcs.erl | 4 ++++
 apps/emqx_rule_engine/src/emqx_rule_utils.erl | 1 +
 2 files changed, 5 insertions(+)

diff --git a/apps/emqx_rule_engine/src/emqx_rule_funcs.erl b/apps/emqx_rule_engine/src/emqx_rule_funcs.erl
index 4f8851d40..a96ee7a62 100644
--- a/apps/emqx_rule_engine/src/emqx_rule_funcs.erl
+++ b/apps/emqx_rule_engine/src/emqx_rule_funcs.erl
@@ -35,6 +35,7 @@
         , contains_topic/3
         , contains_topic_match/2
         , contains_topic_match/3
+        , null/0
         ]).
 
 %% Arithmetic Funcs
@@ -300,6 +301,9 @@ find_topic_filter(Filter, TopicFilters, Func) ->
         throw:Result -> Result
     end.
 
+null() ->
+    undefined.
+
 %%------------------------------------------------------------------------------
 %% Arithmetic Funcs
 %%------------------------------------------------------------------------------
diff --git a/apps/emqx_rule_engine/src/emqx_rule_utils.erl b/apps/emqx_rule_engine/src/emqx_rule_utils.erl
index ff7ee0304..3791b1386 100644
--- a/apps/emqx_rule_engine/src/emqx_rule_utils.erl
+++ b/apps/emqx_rule_engine/src/emqx_rule_utils.erl
@@ -228,6 +228,7 @@ tcp_connectivity(Host, Port, Timeout) ->
 unwrap(<<"${", Val/binary>>) ->
     binary:part(Val, {0, byte_size(Val)-1}).
 
+sql_data(undefined) -> null;
 sql_data(List) when is_list(List) -> List;
 sql_data(Bin) when is_binary(Bin) -> Bin;
 sql_data(Num) when is_number(Num) -> Num;