PragmaTwice commented on code in PR #1852:
URL: https://github.com/apache/kvrocks/pull/1852#discussion_r1374420514


##########
src/types/json.h:
##########
@@ -215,6 +218,80 @@ struct JsonValue {
     return Status::OK();
   }
 
+  StatusOr<bool> Merge(const std::string_view path, const std::string 
&merge_value) {
+    bool is_updated = false;
+    const std::string json_root_path = "$";
+    try {
+      jsoncons::json patch_value = jsoncons::json::parse(merge_value);
+      bool not_exists = jsoncons::jsonpath::json_query(value, path).empty();
+
+      if (path == json_root_path || not_exists) {
+        // For non-existing keys the path must be $
+        if (not_exists) {
+          // Create an actual object from non-existing path
+          jsoncons::json created_object = GenerateJsonFromPath(path.data(), 
patch_value);
+
+          // Merge it with patch value
+          auto patch = jsoncons::mergepatch::from_diff(patch_value, 
created_object);
+          jsoncons::mergepatch::apply_merge_patch(patch_value, patch);
+        }
+
+        // Merge with the root. Patch function complies with RFC7396 Json 
Merge Patch
+        jsoncons::mergepatch::apply_merge_patch(value, patch_value);
+        is_updated = true;
+      } else if (!patch_value.is_null()) {
+        // Replace value by path
+        jsoncons::jsonpath::json_replace(
+            value, path, [&patch_value, &is_updated](const std::string & 
/*path*/, jsoncons::json &target) {
+              target = patch_value;
+              is_updated = true;
+            });
+      } else {
+        // Handle null case
+        // Unify path expression.
+        auto expr = jsoncons::jsonpath::make_expression<jsoncons::json>(path);
+        std::string converted_path;
+        expr.evaluate(
+            value, [&](const jsoncons::string_view &p, const jsoncons::json 
&val) { converted_path = p; },
+            jsoncons::jsonpath::result_options::path);
+        // Unify object state
+        jsoncons::json flattened = jsoncons::jsonpath::flatten(value);
+        if (flattened.contains(converted_path)) {
+          flattened.erase(converted_path);
+          value = jsoncons::jsonpath::unflatten(flattened);
+          is_updated = true;
+        }
+      }
+    } catch (const jsoncons::jsonpath::jsonpath_error &e) {
+      return {Status::NotOK, e.what()};
+    } catch (const jsoncons::ser_error &e) {
+      return {Status::NotOK, e.what()};
+    }
+
+    return is_updated;
+  }
+
+  static jsoncons::json GenerateJsonFromPath(const std::string &path, const 
jsoncons::json &value) {
+    std::vector<std::string> parts;
+    std::stringstream ss(path);
+    std::string part;
+
+    while (std::getline(ss, part, '.')) {
+      if (part != "$") {
+        parts.push_back(part);
+      }
+    }
+
+    jsoncons::json result = value;
+    for (auto it = parts.rbegin(); it != parts.rend(); ++it) {
+      jsoncons::json obj;
+      obj[*it] = result;
+      result = obj;
+    }
+
+    return result;

Review Comment:
   Seems it is not general enough, e.g. it cannot process path like `$[0]`, 
`$["hello"]` or `$..a`. 
   I think here we can just use `Get`.



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