Use json array in consumer-producer to save fields order

common/consumertable.cpp

@@ -65,10 +65,11 @@ void ConsumerTable::pop(KeyOpFieldsValuesTuple &kco)
         "local ret = {key, op}\n"
 
         "local jj = cjson.decode(value)\n"
+        "local size = #jj\n"
 
-        "for k,v in pairs(jj) do\n"
-        "    table.insert(ret, k)\n"
-        "    table.insert(ret, v)\n"
+        "for idx=1,size,2 do\n"
+        "    table.insert(ret, jj[idx])\n"
+        "    table.insert(ret, jj[idx+1])\n"
         "end\n"
 
         "if op == 'get' or op == 'getresponse' then\n"

common/json.cpp

@@ -10,11 +10,13 @@ namespace swss {
 
 string JSon::buildJson(const vector<FieldValueTuple> &fv)
 {
-    nlohmann::json j;
+    nlohmann::json j = nlohmann::json::array();
 
+    // we use array to save order
     for (auto &i : fv)
     {
-        j[fvField(i)] = fvValue(i);
+        j.push_back(fvField(i));
+        j.push_back(fvValue(i));
     }
 
     return j.dump();
@@ -26,12 +28,10 @@ void JSon::readJson(const string &jsonstr, vector<FieldValueTuple> &fv)
 
     FieldValueTuple e;
 
-    std::map<std::string, nlohmann::json> m = j;
-
-    for (auto&& kv : m)
+    for (size_t i = 0; i < j.size(); i+=2)
     {
-        fvField(e) = kv.first;
-        fvValue(e) = kv.second;
+        fvField(e) = j[i];
+        fvValue(e) = j[i+1];
         fv.push_back(e);
     }
 }

tests/redis_ut.cpp

@@ -62,20 +62,7 @@ void validateFields(const string& key, const vector<FieldValueTuple>& f)
     int i = 0;
     EXPECT_EQ(maxNumOfFields, f.size());
 
-    // since we are using cjson in lua script
-    // retrived fields order is different than producer
-    // since value is passed as json, order does not matter
-    // but we need to compensate it here
-
-    auto copy = f;
-
-    std::sort(copy.begin(), copy.end(),
-            [](const FieldValueTuple & a, const FieldValueTuple & b) -> bool
-            {
-            return readNumberAtEOL(fvField(a)) < readNumberAtEOL(fvField(b));
-            });
-
-    for (auto fv : copy)
+    for (auto fv : f)
     {
         EXPECT_EQ(i, readNumberAtEOL(fvField(fv)));
         EXPECT_EQ(i, readNumberAtEOL(fvValue(fv)));