Spark ML – Model Persistence

R/ml_persistence.R

ml-persistence

Description

Save/load Spark ML objects

Usage

ml_save(x, path, overwrite = FALSE, ...) 

## S3 method for class 'ml_model'
ml_save( 
  x, 
  path, 
  overwrite = FALSE, 
  type = c("pipeline_model", "pipeline"), 
  ... 
) 

ml_load(sc, path) 

Arguments

Arguments	Description
x	A ML object, which could be a ml_pipeline_stage or a ml_model
path	The path where the object is to be serialized/deserialized.
overwrite	Whether to overwrite the existing path, defaults to FALSE.
…	Optional arguments; currently unused.
type	Whether to save the pipeline model or the pipeline.
sc	A Spark connection.

Value

ml_save() serializes a Spark object into a format that can be read back into sparklyr or by the Scala or PySpark APIs. When called on ml_model objects, i.e. those that were created via the tbl_spark - formula signature, the associated pipeline model is serialized. In other words, the saved model contains both the data processing (RFormulaModel) stage and the machine learning stage.

ml_load() reads a saved Spark object into sparklyr. It calls the correct Scala load method based on parsing the saved metadata. Note that a PipelineModel object saved from a sparklyr ml_model via ml_save() will be read back in as an ml_pipeline_model, rather than the ml_model object.