[PR] feat: support subscribe partition in cpp binding [fluss-rust]

["luoyuxia (via GitHub)" <gi...@apache.org>]

luoyuxia opened a new pull request, #236:
URL: https://github.com/apache/fluss-rust/pull/236

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Re: [PR] feat: support subscribe partition in cpp binding [fluss-rust]

["luoyuxia (via GitHub)" <gi...@apache.org>]

luoyuxia merged PR #236:
URL: https://github.com/apache/fluss-rust/pull/236


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Re: [PR] feat: support subscribe partition in cpp binding [fluss-rust]

["Copilot (via GitHub)" <gi...@apache.org>]

Copilot commented on code in PR #236:
URL: https://github.com/apache/fluss-rust/pull/236#discussion_r2762417891


##########
bindings/cpp/src/table.cpp:
##########
@@ -265,6 +265,15 @@ Result LogScanner::Subscribe(const std::vector<BucketSubscription>& bucket_offse
     return utils::from_ffi_result(ffi_result);
 }
 
+Result LogScanner::SubscribePartition(int64_t partition_id, int32_t bucket_id, int64_t start_offset) {
+    if (!Available()) {
+        return utils::make_error(1, "LogScanner not available");
+    }
+

Review Comment:
   `SubscribePartition` passes `partition_id` straight through to the Rust FFI. On the Rust side, `-1` currently has a special meaning (it routes to the non-partition `subscribe` path), so calling `SubscribePartition(-1, ...)` will not do what the API name implies. Consider validating `partition_id` here (e.g., reject negative values) to prevent surprising behavior at the C++ API boundary.
   ```suggestion
   
       if (partition_id < 0) {
           return utils::make_error(2, "partition_id must be non-negative");
       }
   ```



##########
bindings/cpp/src/lib.rs:
##########
@@ -790,6 +819,15 @@ impl LogScanner {
         }
     }
 
+    fn subscribe_partition(
+        &self,
+        partition_id: i64,
+        bucket_id: i32,
+        start_offset: i64,
+    ) -> ffi::FfiResult {

Review Comment:
   `subscribe_partition` forwards `partition_id` into `do_subscribe`, where `-1` is treated as a sentinel meaning “no partition” and will call `subscribe` instead of `subscribe_partition`. This makes `partition_id = -1` behave unexpectedly for callers and leaks an internal sentinel into the public FFI API. Add an explicit validation in `subscribe_partition` (e.g., reject `partition_id < 0` with a clear error) and/or refactor `do_subscribe` to take `Option<PartitionId>` so the sentinel value is not part of the value space.
   ```suggestion
       ) -> ffi::FfiResult {
           if partition_id < 0 {
               return err_result(1, "partition_id must be non-negative".to_string());
           }
   ```



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