2rueSid commented on code in PR #1852:
URL: https://github.com/apache/kvrocks/pull/1852#discussion_r1382587401
##########
src/types/json.h:
##########
@@ -253,6 +255,54 @@ 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 (not_exists) {
+ // TODO:: Add ability to create an object from path.
+ return {Status::NotOK, "Path does not exist."};
+ }
+
+ if (path == json_root_path) {
+ // 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;
+ }
Review Comment:
We need to delete the key if the merge value is `null`. Since `json_replace`
does not provide access to the parent keys, we cannot use it in this case.
Consider the following example:
```bash
redis> JSON.SET doc $ '{"a":2}'
OK
redis> JSON.MERGE doc $.a 'null'
OK
redis> JSON.GET doc $
```
In the `json_replace` function with this path, we would retrieve the value
of `a`. However, to call the `erase()` function, we need to pass a key name,
and the key `a` cannot point to itself. Therefore, to erase it, we need to have
access to the parent key.
We need something like this:
```cpp
json_replace("{\"a\": 2}", path="$", pseudo_cb={
// This callback function attempts to erase the key 'a' from the JSON
object.
value.erase("$.a");
})
```
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