feat: Enforce backend-owned schema model for Lance directory and REST catalogs

rust/error.rs

@@ -67,6 +67,9 @@ pub enum ErrorCode {
     Exec = 52,
     DatasetMerge = 53,
     NamespaceQueryTable = 54,
+    NamespaceListNamespaces = 55,
+    NamespaceCreateNamespace = 56,
+    NamespaceDropNamespace = 57,
 }
 
 struct LastError {

rust/ffi/dir_namespace.rs

@@ -15,7 +15,8 @@ use crate::runtime;
 use super::session::record_dataset_open;
 use super::types::DatasetHandle;
 use super::util::{
-    cstr_to_str, optional_session_handle, slice_from_ptr, to_c_string, FfiError, FfiResult,
+    cstr_to_str, export_string_list, optional_session_handle, slice_from_ptr, to_c_string,
+    FfiError, FfiResult, LanceStringList,
 };
 
 fn parse_storage_options(
@@ -102,18 +103,10 @@ pub unsafe extern "C" fn lance_dir_namespace_list_tables(
     option_keys: *const *const c_char,
     option_values: *const *const c_char,
     options_len: usize,
-) -> *const c_char {
-    match dir_namespace_list_tables_inner(root, option_keys, option_values, options_len) {
-        Ok(tables) => {
-            clear_last_error();
-            let joined = tables.join("\n");
-            to_c_string(joined).into_raw() as *const c_char
-        }
-        Err(err) => {
-            set_last_error(err.code, err.message);
-            ptr::null()
-        }
-    }
+    out: *mut LanceStringList,
+) -> i32 {
+    let result = dir_namespace_list_tables_inner(root, option_keys, option_values, options_len);
+    unsafe { export_string_list(result, out) }
 }
 
 fn open_dataset_in_dir_namespace_inner(

rust/ffi/index.rs

@@ -20,7 +20,8 @@ use crate::runtime;
 
 use super::types::{SchemaHandle, StreamHandle};
 use super::util::{
-    canonicalize_lance_field_path, cstr_to_str, dataset_handle, to_c_string, FfiError, FfiResult,
+    canonicalize_lance_field_path, cstr_to_str, dataset_handle, export_string_list, to_c_string,
+    FfiError, FfiResult, LanceStringList,
 };
 
 #[derive(Debug, Default, Deserialize)]
@@ -156,50 +157,15 @@ fn create_index_list_stream_inner(dataset: *mut c_void) -> FfiResult<StreamHandl
     Ok(StreamHandle::Batches(vec![batch].into_iter()))
 }
 
-/// Returns an array of column names that have scalar indices.
-/// The caller must free the returned array with `lance_free_scalar_indexed_columns`.
+/// Returns column names that have scalar indices.
+/// The caller must free the result with `lance_free_string_list`.
 #[no_mangle]
 pub unsafe extern "C" fn lance_dataset_list_scalar_indexed_columns(
     dataset: *mut c_void,
-    out_len: *mut usize,
-) -> *mut *mut c_char {
-    match list_scalar_indexed_columns_inner(dataset) {
-        Ok(cols) => {
-            clear_last_error();
-            unsafe { *out_len = cols.len() };
-            if cols.is_empty() {
-                return std::ptr::null_mut();
-            }
-            let ptrs: Vec<*mut c_char> = cols
-                .into_iter()
-                .map(|s| to_c_string(s).into_raw())
-                .collect();
-            let mut boxed = ptrs.into_boxed_slice();
-            let ptr = boxed.as_mut_ptr();
-            std::mem::forget(boxed);
-            ptr
-        }
-        Err(err) => {
-            set_last_error(err.code, err.message);
-            unsafe { *out_len = 0 };
-            std::ptr::null_mut()
-        }
-    }
-}
-
-#[no_mangle]
-pub unsafe extern "C" fn lance_free_scalar_indexed_columns(ptr: *mut *mut c_char, len: usize) {
-    if ptr.is_null() {
-        return;
-    }
-    unsafe {
-        let slice = Box::from_raw(std::ptr::slice_from_raw_parts_mut(ptr, len));
-        for &p in slice.iter() {
-            if !p.is_null() {
-                drop(std::ffi::CString::from_raw(p));
-            }
-        }
-    }
+    out: *mut LanceStringList,
+) -> i32 {
+    let result = list_scalar_indexed_columns_inner(dataset);
+    unsafe { export_string_list(result, out) }
 }
 
 fn list_scalar_indexed_columns_inner(dataset: *mut c_void) -> FfiResult<Vec<String>> {