element

const RelIDOffset = -1e17

RelIDOffset is a constant we subtract from relation IDs to avoid conflicts with way and node IDs. Nodes, ways and relations have separate ID spaces in OSM, but we need unique IDs for updating and removing elements in diff mode. In a normal diff import relation IDs are negated to distinguish them from way IDs, because ways and relations can both be imported in the same polygon table. Nodes are only imported together with ways and relations in single table imports (see `type_mappings`). In this case we negate the way and relation IDs and aditionaly subtract RelIDOffset from the relation IDs. Ways will go from -0 to -100,000,000,000,000,000, relations from -100,000,000,000,000,000 down wards.