reference a value from other linked table2

common/src/proto/komp_ac.tables_data.rs

@@ -168,6 +168,11 @@ pub struct PutTableDataRequest {
     ///   FAILED_PRECONDITION, instructing the caller to include X explicitly.
     ///
     /// Passing an empty map results in a no-op success response.
+    /// A LINK may be supplied as {"id": "42", "version": "2"} to explicitly
+    /// accept its target's current version, even when the row id is unchanged.
+    /// Both values must be positive integers. The server rejects a stale version
+    /// and atomically updates the saved FK version and all its stored linked values.
+    /// A plain unchanged row id preserves the previously saved version and values.
     #[prost(map = "string, message", tag = "4")]
     pub data: ::std::collections::HashMap<
         ::prost::alloc::string::String,