Add migration to support z16 metatiling

data/migrations/v0.8.0-adjust-toi-for-z16-metatiling.py

@@ -0,0 +1,34 @@
+from redis import StrictRedis
+from tilequeue.cache import RedisCacheIndex
+from tilequeue.config import make_config_from_argparse
+from tilequeue.tile import coord_marshall_int
+from tilequeue.tile import coord_unmarshall_int
+import sys
+
+if len(sys.argv) > 1:
+    cfg_path = sys.argv[1]
+else:
+    cfg_path = '/etc/tilequeue/config.yaml'
+
+cfg = make_config_from_argparse(cfg_path)
+redis_client = StrictRedis(cfg.redis_host)
+cache_index = RedisCacheIndex(redis_client)
+tiles_of_interest = cache_index.fetch_tiles_of_interest()
+
+coord_ints_to_add = set()
+for coord_int in tiles_of_interest:
+    coord = coord_unmarshall_int(coord_int)
+    if coord.zoom > 16:
+        coord_at_z16 = coord.zoomTo(16).container()
+        coord_int_at_z16 = coord_marshall_int(coord_at_z16)
+        coord_ints_to_add.add(coord_int_at_z16)
+
+batch_size = 100
+buf = []
+for coord_int in coord_ints_to_add:
+    buf.append(coord_int)
+    if len(buf) >= batch_size:
+        redis_client.sadd(cache_index.cache_set_key, *buf)
+        del buf[:]
+if buf:
+    redis_client.sadd(cache_index.cache_set_key, *buf)