text: -- mbtiles schema
  
  BEGIN;
  
  CREATE TABLE indexdata (name text, value text);
  CREATE TABLE tiles (zoom_level integer, tile_column integer, tile_row integer, tile_data blob);
  CREATE TABLE grids (zoom_level integer, tile_column integer, tile_row integer, grid blob);
  CREATE TABLE grid_data (zoom_level integer, tile_column integer, tile_row integer, key_name text, key_json text);
  
  COMMIT;