Development notes related to Embedded Databases used in the Playground

Table of contents:

Apache IoTDB

Phase1 PoC

• Versions used for development: Apache IoTDB v1.2.2, Apache Go Client v1.1.7
• Timeseries Schema
  • As there is no mechanism (that we are aware of) for a southbound feeder and WAII to negotiate/communicate a schema as a starting point a simple key/value pair schema was used within IoTDB to store VSS timeseries data. A simple schema is probably the best place to start anyway for simplicity of understanding.

  • The IoTDB data model supports hierarchical paths for efficiency of data at scale. The model uses a dot notation. So for example a vehicle DB may have the hierarchy root.region.model.

  • This causes a challenge integrating VSS node paths which also use a dot notation. For example using the VSS node path Vehicle.CurrentLocation.Longitude as the timeseries key/measurement would cause Vehicle and CurrentLocation to be used in the hierarchy. When scaled across millions of vehicles this would cause inefficiency in storage and retrieval.

  • A simple solution is to quote the VSS node path and is what used here.

    • Example: Using the Go Client the VSS node Vehicle.CurrentLocation.Longitude is back quoted and suffixed to the IoTDB timeseries path, e.g. root.region.model.`Vehicle.CurrentLocation.Longitude`

    • Example: querying stored last VSS value using the IoTDB Cli client:

    • Code Block
      language sql
      ---------------------

      
      

      Starting IoTDB Cli

      
      

      ---------------------

      
      

      _____       _________  ______   ______

      
      

      |_   _|     |  _   _  ||_   _ `.|_   _ \

      
      

      | |   .--.|_/ | | \_|  | | `. \ | |_) |

      
      

      | | / .'`\ \  | |      | |  | | |  __'.

      
      

      _| |_| \__. | _| |_    _| |_.' /_| |__) |

      
      

      |_____|'.__.' |_____|  |______.'|_______/  version 1.2.2 (Build: 5d0bfb0)

      
      
      

      Successfully login at iotdb-service:6667

      
      

      IoTDB> select last `Vehicle.CurrentLocation.Longitude` from root.test2.dev1

      
      

      +------------------------+---------------------------------------------------+--------+--------+

      
      

      |                    Time|                                         Timeseries|   Value|DataType|

      
      

      +------------------------+---------------------------------------------------+--------+--------+

      
      

      |2024-02-01T19:57:37.604Z|root.test2.dev1.`Vehicle.CurrentLocation.Longitude`|-73.9873|   FLOAT|

      
      

      +------------------------+---------------------------------------------------+--------+--------+

      
      

      Total line number = 1

      
      

      It costs 0.177s

      
      IoTDB> 
      .

      IoTDB>

• Creating VSS aligned timeseries

  • Code Block
    language sql title Examples of creating a schema for an aligned VSS timeseries using SQL
    CREATE ALIGNED TIMESERIES root.test2.dev1(`Vehicle.CurrentLocation.Longitude` FLOAT, `Vehicle.CurrentLocation.Longitude` FLOAT, `Vehicle.Cabin.Infotainment.HMI.DistanceUnit` TEXT) CREATE ALIGNED TIMESERIES root.test2.dev1(`Vehicle.CurrentLocation.Longitude` FLOAT encoding=PLAIN compressor=SNAPPY, `Vehicle.CurrentLocation.Longitude` FLOAT encoding=PLAIN compressor=SNAPPY, `Vehicle.Cabin.Infotainment.HMI.DistanceUnit` TEXT encoding=PLAIN compressor=SNAPPY)

    
    

MongoDB Realm