This topic describes how to use DLA Ganos to load raster data from PolarDB.
Procedure
- Initialize a Spark session.
val spark: SparkSession = { val session = SparkSession.builder .master("local[*]") .withKryoSerialization .config(additionalConf) .getOrCreate() session } // Load the Raster driver of DLA Ganos. spark.withGanosRaster
- Initialize connection parameters.
val options = Map( "url" -> "jdbc:postgresql://121.43.XX.XX:5432/ganos_demodb", "user" -> "postgres", "password" -> "Ganos@2020", "dbtable" -> "gf", "numPartitions" -> "4")val options = Map( "url" -> "jdbc:postgresql://121.43.XX.XX:5432/ganos_demodb", "user" -> "postgres", "password" -> "Ganos@2020", "dbtable" -> "gf", "numPartitions" -> "4")
- Load the catalog table.
val cat = spark.read.ganos.polardbRasterCatalog(options)
- View the results.
The catalog table contains the IDs of layers and metadata, and supports spatio-temporal queries.
- You can specify the ID and zoom to load a specific layer. The default value of z is
0, which indicates the lowest level of the pyramid.
val layer = spark.read.ganos.polardbRasterImage(options).load(id, zoom)
Important Multi-band images are automatically split into multiple single-band tiles for display. - You can also load multiple layers at the same time based on the collection of layer
IDs.
val layers = spark.read.ganos.polardbRasterCover(options).load(Seq[id], zoom)
- You can specify the ID and zoom to load a specific layer. The default value of z is
0, which indicates the lowest level of the pyramid.