feat(frontend): expose Vnode function as __rw_vnode for easy debu…

…gging (#4327)

* expose internal `vnode` function as `__rw_vnode` for debugging

* add e2e test for `__rw_vnode` just to make sure the function runs

Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

e2e_test/batch/functions/internal.slt.part

@@ -0,0 +1,17 @@
+statement ok
+SET RW_IMPLICIT_FLUSH TO true;
+
+statement ok
+create table t(v1 varchar, v2 int, v3 int)
+
+statement ok
+select __rw_vnode(_row_id) as vnode, _row_id from t;
+
+statement ok
+insert into t values ('aaa', 1, 1), ('bbb', 0, 2), ('ccc', 0, 5), ('ddd', 1, 4)
+
+statement ok
+select __rw_vnode(_row_id) as vnode, _row_id from t;
+
+statement ok
+drop table t

src/frontend/src/binder/expr/function.rs

@@ -154,6 +154,7 @@ impl Binder {
             "current_database" if inputs.is_empty() => {
                 return Ok(ExprImpl::literal_varchar(self.db_name.clone()));
             }
+            "__rw_vnode" => ExprType::Vnode,
             _ => {
                 return Err(ErrorCode::NotImplemented(
                     format!("unsupported function: {:?}", function_name),