port freeze function to python

nominatim/tools/freeze.py

@@ -0,0 +1,43 @@
+"""
+Functions for removing unnecessary data from the database.
+"""
+from pathlib import Path
+
+UPDATE_TABLES = [
+    'address_levels',
+    'gb_postcode',
+    'import_osmosis_log',
+    'import_polygon_%',
+    'location_area%',
+    'location_road%',
+    'place',
+    'planet_osm_%',
+    'search_name_%',
+    'us_postcode',
+    'wikipedia_%'
+]
+
+def drop_update_tables(conn):
+    """ Drop all tables only necessary for updating the database from
+        OSM replication data.
+    """
+
+    where = ' or '.join(["(tablename LIKE '{}')".format(t) for t in UPDATE_TABLES])
+
+    with conn.cursor() as cur:
+        cur.execute("SELECT tablename FROM pg_tables WHERE " + where)
+        tables = [r[0] for r in cur]
+
+        for table in tables:
+            cur.execute('DROP TABLE IF EXISTS "{}" CASCADE'.format(table))
+
+    conn.commit()
+
+
+def drop_flatnode_file(fname):
+    """ Remove the flatnode file if it exists.
+    """
+    if fname:
+        fpath = Path(fname)
+        if fpath.exists():
+            fpath.unlink()