sparklyudf: Scala UDF from R - Example

sparklyudf demonstrates how to build a sparklyr extension package that uses custom Scala code which is compiled, deployed to Apache Spark and registered as an UDF that can be used in SQL and dplyr.

Building

First build this package, then build its Spark 2.0 jars by running:

spec <- sparklyr::spark_default_compilation_spec()
spec <- Filter(function(e) e$spark_version >= "2.0.0", spec)
sparklyr::compile_package_jars()

then build the R package as usual.

This package contains an Scala-based UDF defined as:

object Main {
  def register_hello(spark: SparkSession) = {
    spark.udf.register("hello", (name: String) => {
      "Hello, " + name + "! - From Scala"
    })
  }
}

Getting Started

Connect and test this package as follows:

library(sparklyudf)
library(sparklyr)
library(dplyr)

## 
## Attaching package: 'dplyr'

## The following objects are masked from 'package:stats':
## 
##     filter, lag

## The following objects are masked from 'package:base':
## 
##     intersect, setdiff, setequal, union

sc <- spark_connect(master = "local")

## * Using Spark: 2.1.0

sparklyudf_register(sc)

## <jobj[13]>
##   class org.apache.spark.sql.expressions.UserDefinedFunction
##   UserDefinedFunction(<function1>,StringType,Some(List(StringType)))

Now the Scala UDF hello() is registered and can be used as follows:

data.frame(name = "Javier") %>%
  copy_to(sc, .) %>%
  mutate(hello = hello(name))

## # Source:   lazy query [?? x 2]
## # Database: spark_connection
##     name                       hello
##    <chr>                       <chr>
## 1 Javier Hello, Javier! - From Scala

spark_disconnect_all()

## [1] 1