Save data to external storage
WherobotsDB has APIs that can save an entire raster column to files in a specified location.
Save In-DB Raster¶
Before saving, the raster type column needs to be converted to a binary format. WherobotsDB provides several functions to convert a raster column into a binary column suitable for file storage. Once in binary format, the raster data can then be written to files on disk using the WherobotsDB file storage APIs.
rasterDf.write.format("raster").option("rasterField", "raster").option("fileExtension", ".tiff").mode(SaveMode.Overwrite).save(dirPath)
WherobotsDB has a few writer functions that create the binary DataFrame necessary for saving the raster images.
As Arc Grid¶
Use RS_AsArcGrid to get binary Dataframe of raster in Arc Grid format.
SELECT RS_AsArcGrid(raster)
As GeoTiff¶
Use RS_AsGeoTiff to get binary Dataframe of raster in GeoTiff format.
SELECT RS_AsGeoTiff(raster)
As PNG¶
Use RS_AsPNG to get binary Dataframe of raster in PNG format.
SELECT RS_AsPNG(raster)
Please refer to Raster writer docs for more details.
Save Out-DB Raster¶
Out-DB raster must be saved in a Havasu (Iceberg) table. For more information, please refer to the Havasu documentation. Or, users can use RS_AsInDB to convert the out-db raster to in-db raster, and then save them to files.