selecting a range of elements in an array spark sql

Question

I use spark-shell to do the below operations.

Recently loaded a table with an array column in spark-sql .

Here is the DDL for the same:

Answer 1

Here is a solution using a User Defined Function which has the advantage of working for any slice size you want. It simply builds a UDF function around the scala builtin slice method :

import sqlContext.implicits._
import org.apache.spark.sql.functions._

val slice = udf((array : Seq[String], from : Int, to : Int) => array.slice(from,to))

Example with a sample of your data :

val df = sqlContext.sql("select array('Jon', 'Snow', 'Castle', 'Black', 'Ned') as emp_details")
df.withColumn("slice", slice($"emp_details", lit(0), lit(3))).show

Produces the expected output

+--------------------+-------------------+
|         emp_details|              slice|
+--------------------+-------------------+
|[Jon, Snow, Castl...|[Jon, Snow, Castle]|
+--------------------+-------------------+

You can also register the UDF in your sqlContext and use it like this

sqlContext.udf.register("slice", (array : Seq[String], from : Int, to : Int) => array.slice(from,to))
sqlContext.sql("select array('Jon','Snow','Castle','Black','Ned'),slice(array('Jon‌​','Snow','Castle','Black','Ned'),0,3)")

You won't need lit anymore with this solution