NodeData._node_data is None means event body not yet fetched

NodeData._node_data is None means event body not yet fetched; accessing .data triggers lazy nodestore RPC. BaseEvent.message always hits nodestore — use obj._snuba_data.get('message') to avoid. Batch optimization: bind_nodes() replaces N RPCs with 1 get_multi. ClickHouse returns '' not NULL for missing Nullable string columns — filter both '' and None. Snuba message column is search_message (processed), not the real event message. Discover column names (user.id, user.email, event.type) differ from Event._snuba_data keys (user_id, email, type) — remap when constructing Event(snuba_data={...}).