port check-for-update function to python

nominatim/cli.py

@@ -257,14 +257,16 @@ class UpdateReplication:
             return 0
 
         if args.check_for_updates:
-            params.append('--check-for-updates')
+            ret = replication.check_for_updates(conn, args.config.REPLICATION_URL)
+            conn.close()
+            return ret
+
+        if args.once:
+            params.append('--import-osmosis')
         else:
-            if args.once:
-                params.append('--import-osmosis')
-            else:
-                params.append('--import-osmosis-all')
-            if not args.do_index:
-                params.append('--no-index')
+            params.append('--import-osmosis-all')
+        if not args.do_index:
+            params.append('--no-index')
 
         return run_legacy_script(*params, nominatim_env=args)
 

nominatim/db/status.py

@@ -48,3 +48,16 @@ def set_status(conn, date, seq=None, indexed=True):
                        VALUES (%s, %s, %s)""", (date, seq, indexed))
 
     conn.commit()
+
+
+def get_status(conn):
+    """ Return the current status as a triple of (date, sequence, indexed).
+        If status has not been set up yet, a triple of None is returned.
+    """
+    with conn.cursor() as cur:
+        cur.execute("SELECT * FROM import_status LIMIT 1")
+        if cur.rowcount < 1:
+            return None, None, None
+
+        row = cur.fetchone()
+        return row['lastimportdate'], row['sequence_id'], row['indexed']

nominatim/tools/replication.py

@@ -32,3 +32,28 @@ def init_replication(conn, base_url):
     status.set_status(conn, date=date, seq=seq)
 
     LOG.warning("Updates intialised at sequence %s (%s)", seq, date)
+
+
+def check_for_updates(conn, base_url):
+    """ Check if new data is available from the replication service at the
+        given base URL.
+    """
+    _, seq, _ = status.get_status(conn)
+
+    if seq is None:
+        LOG.error("Replication not set up. "
+                  "Please run 'nominatim replication --init' first.")
+        return 254
+
+    state = ReplicationServer(base_url).get_state_info()
+
+    if state is None:
+        LOG.error("Cannot get state for URL %s.", base_url)
+        return 253
+
+    if state.sequence <= seq:
+        LOG.warning("Database is up to date.")
+        return 1
+
+    LOG.warning("New data available (%i => %i).", seq, state.sequence)
+    return 0