add skeleton code for convert function

nominatim/tools/convert_sqlite.py

@@ -0,0 +1,30 @@
+# SPDX-License-Identifier: GPL-3.0-or-later
+#
+# This file is part of Nominatim. (https://nominatim.org)
+#
+# Copyright (C) 2023 by the Nominatim developer community.
+# For a full list of authors see the git log.
+"""
+Exporting a Nominatim database to SQlite.
+"""
+from typing import Set
+from pathlib import Path
+
+import sqlalchemy as sa
+
+import nominatim.api as napi
+
+async def convert(project_dir: Path, outfile: Path, options: Set[str]) -> None:
+    """ Export an existing database to sqlite. The resulting database
+        will be usable against the Python frontend of Nominatim.
+    """
+    api = napi.NominatimAPIAsync(project_dir)
+
+    try:
+        outapi = napi.NominatimAPIAsync(project_dir,
+                                        {'NOMINATIM_DATABASE_DSN': f"sqlite:dbname={outfile}"})
+
+        async with api.begin() as inconn, outapi.begin() as outconn:
+            pass
+    finally:
+        await api.close()