Add command-line parameter for enabling distance cache.

include/contractor/contractor_config.hpp

@@ -72,8 +72,14 @@ struct ContractorConfig final : storage::IOConfig
     // The remaining vertices form the core of the hierarchy
     //(e.g. 0.8 contracts 80 percent of the hierarchy, leaving a core of 20%)
     double core_factor;
+
+    // Whether to store distances for CH edges in addition to duration/weight
+    // Defaults to false.  Setting to true will require more storage/memory,
+    // but avoids the need for path unpacking to learn the distance of a CH
+    // route (useful for faster distance results in table queries)
+    bool cache_distances;
 };
-}
-}
+} // namespace contractor
+} // namespace osrm
 
 #endif // EXTRACTOR_OPTIONS_HPP

src/tools/contract.cpp

@@ -81,7 +81,8 @@ return_code parseArguments(int argc,
         "time-zone-file",
         boost::program_options::value<std::string>(&contractor_config.updater_config.tz_file_path),
         "Required for conditional turn restriction parsing, provide a geojson file containing "
-        "time zone boundaries");
+        "time zone boundaries")("cache-distances",boost::program_options::bool_switch(&contractor_config.cache_distances)->default_value(false),
+        "Store distances for CH edges, avoiding the need for query-time re-calculation.");
 
     // hidden options, will be allowed on command line, but will not be shown to the user
     boost::program_options::options_description hidden_options("Hidden options");