Add last update column

README.md

@@ -27,6 +27,7 @@ Please add a small reasoning around the following points for each proposed merge
 | relation_id | integer                   |
 | quadkey     | char(18)                  |
 | occupancy   | text                      |
+| last_update | timestamp                 |
 
 #### `migrations` - Information about database migrations
 

migrations/00010_add_column_last_update.sql

+ALTER TABLE public.obm_buildings
+ADD COLUMN IF NOT EXISTS last_update TIMESTAMP;
+CREATE INDEX idx_last_update
+ON public.obm_buildings(last_update);