Instr function in Spark with 3 arguments

Question

I have a problem with using instr() function in Spark. The definition of function looks like below: instr(Column str, String substring)

I want to use instr in the same way as it is in Impala like:

instr(Column str, String substring, Int [position]) - return index position

In spark we option to give only 2 parameters, but i need to use 3rd parameter with int value basically (-1)

Col has value like

SNNNN NNNNN NNSNN SNSNS NNNNS

Expected code:- instr("ColName", "S", -1) Expected result :- 1 0 3 5 5

Answer 1

If you wanted to go with -ve position number, substring_index + length might be helpful as below-

 val frame = Seq("SNNNN","NNNNN","NNSNN","SNSNS","NNNNS").toDF("values")
    frame.withColumn("x", length($"values") - length(substring_index($"values", "S", -1)))
      .show(false)
    /**
      * +------+---+
      * |values|x  |
      * +------+---+
      * |SNNNN |1  |
      * |NNNNN |0  |
      * |NNSNN |3  |
      * |SNSNS |5  |
      * |NNNNS |5  |
      * +------+---+
      */

Answer 2

Solution using UDF in spark:

import org.apache.spark.sql.types._
import org.apache.spark.sql.functions._
val df = sc.parallelize(Seq("SNNNN","NNNNN","NNSNN","SNSNS","NNNNS")).toDF("values")
val findIndexUDF = udf( (x: String) => (x.lastIndexOf("S")+1))
df.withColumn("indexval", findIndexUDF($"values")).show()
/*+------+--------+
|values|indexval|
+------+--------+
| SNNNN|       1|
| NNNNN|       0|
| NNSNN|       3|
| SNSNS|       5|
| NNNNS|       5|
+------+--------+*/