PragmaTwice commented on code in PR #1852:
URL: https://github.com/apache/kvrocks/pull/1852#discussion_r1381813120
##########
src/types/json.h:
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@@ -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:
Oh, I check the document of JSON.MERGE and now get your point.
I think currently you can just implement the one that is supported by
jsoncons (specifically, the case when a value exists in the jsonpath provided
by the user) and return some error message in other cases. (you can add a
`TODO` comment in the code.)
And after this PR being merged, you can try to cover more cases if you are
interested.
And of course opening a discussion or issue in the jsoncons community to
address this problem is a great idea : )
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