add CSV format for importance import

nominatim/db/utils.py

@@ -92,6 +92,11 @@ class CopyBuffer:
         return self
 
 
+    def size(self) -> int:
+        """ Return the number of bytes the buffer currently contains.
+        """
+        return self.buffer.tell()
+
     def __exit__(self, exc_type: Any, exc_value: Any, traceback: Any) -> None:
         if self.buffer is not None:
             self.buffer.close()
@@ -115,7 +120,10 @@ class CopyBuffer:
 
     def copy_out(self, cur: Cursor, table: str, columns: Optional[Iterable[str]] = None) -> None:
         """ Copy all collected data into the given table.
+
+            The buffer is empty and reusable after this operation.
         """
         if self.buffer.tell() > 0:
             self.buffer.seek(0)
             cur.copy_from(self.buffer, table, columns=columns)
+            self.buffer = io.StringIO()