fix(nested_put): fix a data loss bug introduced by #11172

apps/emqx_rule_engine/src/emqx_rule_runtime.erl

@@ -378,9 +378,9 @@ eval({Op, _} = Exp, Context) when is_list(Context) andalso (Op == path orelse Op
             end
     end;
 eval({path, [{key, <<"payload">>} | Path]}, #{payload := Payload}) ->
-    nested_get({path, Path}, may_decode_payload(Payload));
+    nested_get({path, Path}, maybe_decode_payload(Payload));
 eval({path, [{key, <<"payload">>} | Path]}, #{<<"payload">> := Payload}) ->
-    nested_get({path, Path}, may_decode_payload(Payload));
+    nested_get({path, Path}, maybe_decode_payload(Payload));
 eval({path, _} = Path, Columns) ->
     nested_get(Path, Columns);
 eval({range, {Begin, End}}, _Columns) ->
@@ -410,6 +410,16 @@ eval({'case', CaseOn, CaseClauses, ElseClauses}, Columns) ->
 eval({'fun', {_, Name}, Args}, Columns) ->
     apply_func(Name, [eval(Arg, Columns) || Arg <- Args], Columns).
 
+%% the payload maybe is JSON data, decode it to a `map` first for nested put
+ensure_decoded_payload({path, [{key, payload} | _]}, #{payload := Payload} = Columns) ->
+    Columns#{payload => maybe_decode_payload(Payload)};
+ensure_decoded_payload(
+    {path, [{key, <<"payload">>} | _]}, #{<<"payload">> := Payload} = Columns
+) ->
+    Columns#{<<"payload">> => maybe_decode_payload(Payload)};
+ensure_decoded_payload(_, Columns) ->
+    Columns.
+
 alias({var, Var}, _Columns) ->
     {var, Var};
 alias({const, Val}, _Columns) when is_binary(Val) ->
@@ -497,12 +507,12 @@ add_metadata(Columns, Metadata) when is_map(Columns), is_map(Metadata) ->
 %%------------------------------------------------------------------------------
 %% Internal Functions
 %%------------------------------------------------------------------------------
-may_decode_payload(Payload) when is_binary(Payload) ->
+maybe_decode_payload(Payload) when is_binary(Payload) ->
     case get_cached_payload() of
         undefined -> safe_decode_and_cache(Payload);
         DecodedP -> DecodedP
     end;
-may_decode_payload(Payload) ->
+maybe_decode_payload(Payload) ->
     Payload.
 
 get_cached_payload() ->
@@ -522,7 +532,8 @@ safe_decode_and_cache(MaybeJson) ->
 ensure_list(List) when is_list(List) -> List;
 ensure_list(_NotList) -> [].
 
-nested_put(Alias, Val, Columns) ->
+nested_put(Alias, Val, Columns0) ->
+    Columns = ensure_decoded_payload(Alias, Columns0),
     emqx_rule_maps:nested_put(Alias, Val, Columns).
 
 inc_action_metrics(RuleId, Result) ->

apps/emqx_rule_engine/test/emqx_rule_engine_SUITE.erl

@@ -104,7 +104,8 @@ groups() ->
             t_sqlparse_true_false,
             t_sqlparse_undefined_variable,
             t_sqlparse_new_map,
-            t_sqlparse_invalid_json
+            t_sqlparse_invalid_json,
+            t_sqlselect_as_put
         ]},
         {events, [], [
             t_events,
@@ -1587,6 +1588,45 @@ t_sqlselect_message_publish_event_keep_original_props_2(_Config) ->
     emqtt:stop(Client1),
     delete_rule(TopicRule).
 
+t_sqlselect_as_put(_Config) ->
+    %% Verify SELECT with 'AS' to update the payload
+    Sql =
+        "select payload, "
+        "'STEVE' as payload.data[1].name "
+        "from \"t/#\" ",
+    PayloadMap = #{
+        <<"f1">> => <<"f1">>,
+        <<"f2">> => <<"f2">>,
+        <<"data">> => [
+            #{<<"name">> => <<"n1">>, <<"idx">> => 1},
+            #{<<"name">> => <<"n2">>, <<"idx">> => 2}
+        ]
+    },
+    PayloadBin = emqx_utils_json:encode(PayloadMap),
+    SqlResult = emqx_rule_sqltester:test(
+        #{
+            sql => Sql,
+            context =>
+                #{
+                    payload => PayloadBin,
+                    topic => <<"t/a">>
+                }
+        }
+    ),
+    ?assertMatch({ok, #{<<"payload">> := _}}, SqlResult),
+    {ok, #{<<"payload">> := PayloadMap2}} = SqlResult,
+    ?assertMatch(
+        #{
+            <<"f1">> := <<"f1">>,
+            <<"f2">> := <<"f2">>,
+            <<"data">> := [
+                #{<<"name">> := <<"STEVE">>, <<"idx">> := 1},
+                #{<<"name">> := <<"n2">>, <<"idx">> := 2}
+            ]
+        },
+        PayloadMap2
+    ).
+
 t_sqlparse_event_1(_Config) ->
     Sql =
         "select topic as tp "