Draft: Feature/mongo db

MongoDB implementation of the long-term memory as part of the bachelor thesis of Robin Müller (utwee_mueller).

Tasks:

• implement a Mixin for the MongoDB version of the LTM
  • set-up and connection to database
  • writing into the database
  • reading from the database
  • adjusting keys
• test MongoDBMixin for different memory servers
  • VisionMemory
  • ObjectMemory
  • RobotStateMemory
  • GraspMemory
  • ...
• Implement an autonomous key selection algorithm

source/RobotAPI/libraries/armem/server/ltm/detail/mixins/util/mongodb.cpp

@@ -79,16 +79,26 @@ namespace armarx::armem::server::ltm::util::mongodb
         }
     } // namespace detail
 
-    std::optional<mongocxx::database>
-    databaseExists(mongocxx::client& client, const std::string& databaseName)
-    {
-        //auto names = client.list_databases();
-        //if (auto it = std::find(names.begin(), names.end(), databaseName); it != names.end())
-        //{
-        //    return client[databaseName];
-        //}
-        return std::nullopt;
+    std::optional<mongocxx::database> 
+    databaseExists(mongocxx::client& client, const std::string& databaseName) {
+    // MongoCXX Version > 3.5.0 required 
+    /*
+    auto names = client.list_database_names();
+    if (auto it = std::find(names.begin(), names.end(), databaseName); it != names.end()) {
+        return client[databaseName];
+    }
+    return std::nullopt;
+    */
+
+    // Compatibility with older MongoCXX versions
+    mongocxx::cursor dbs = client.list_databases();
+    for (auto &view : dbs) {
+        if (view["name"].get_utf8().value == databaseName) {
+            return client[databaseName];
+        }
     }
+    return std::nullopt;
+}
 
     mongocxx::database
     ensureDatabaseExists(mongocxx::client& client,