feat: add generated column Python API

python/src/function.rs

@@ -227,8 +227,7 @@ impl AuthoredFunctionCall {
         })
     }
 
-    /// Crate-private accessor for the later table-binding slice.
-    #[allow(dead_code)]
+    /// Crate-private accessor for the exact Function owned by this authored call.
     pub(crate) fn function(&self) -> &lancedb::function::Function {
         &self.function
     }
@@ -243,9 +242,8 @@ impl AuthoredFunctionCall {
     ///
     /// Calls [`lancedb::Table::generated_column_binding_snapshot`] once so the
     /// returned `source_table_version` and canonical [`FunctionCall`] share the
-    /// same field identities and Arrow types. Source version stays outside the
-    /// call for later Job envelope submit. Not yet wired to create/change submit.
-    #[allow(dead_code)] // Bound by the immediately following create/change submit slice.
+    /// same field identities and Arrow types. Source version remains outside the
+    /// call for the create/change Job envelope.
     pub(crate) async fn bind_to_table(
         &self,
         table: &lancedb::Table,

python/src/table.rs

@@ -930,6 +930,39 @@ impl Table {
         })
     }
 
+    /// Hidden bridge: bind an authored Function call once and submit create.
+    ///
+    /// Private native path for Python ``table.add_generated_column``. Rejects an
+    /// empty ``column_name`` before reading the table handle. Does not expose
+    /// source version, stable field IDs, the operation spec, or request envelope.
+    #[doc(hidden)]
+    pub fn _add_generated_column<'a>(
+        self_: PyRef<'a, Self>,
+        column_name: String,
+        call: Bound<'_, crate::function::AuthoredFunctionCall>,
+    ) -> PyResult<Bound<'a, PyAny>> {
+        if column_name.is_empty() {
+            return Err(PyValueError::new_err("column_name must be non-empty"));
+        }
+        let inner = self_.inner_ref()?.clone();
+        let authored = call.get().clone();
+        future_into_py(self_.py(), async move {
+            let (source_table_version, bound_call) =
+                authored.bind_to_table(&inner).await.infer_error()?;
+            let spec = lancedb::function::CreateGeneratedColumnJobSpec::try_new(
+                column_name,
+                authored.function(),
+                bound_call,
+            )
+            .infer_error()?;
+            let job = inner
+                .submit_create_generated_column(source_table_version, spec)
+                .await
+                .infer_error()?;
+            Ok(crate::job::Job::new(job))
+        })
+    }
+
     pub fn drop_index(self_: PyRef<'_, Self>, index_name: String) -> PyResult<Bound<'_, PyAny>> {
         let inner = self_.inner_ref()?.clone();
         future_into_py(self_.py(), async move {