in src/columnar_storage/src/read.rs [166:176]
fn with_new_children(
self: Arc<Self>,
children: Vec<Arc<dyn ExecutionPlan>>,
) -> DfResult<Arc<dyn ExecutionPlan>> {
Ok(Arc::new(MergeExec::new(
Arc::clone(&children[0]),
self.num_primary_keys,
self.value_operator.clone(),
self.keep_builtin,
)))
}