Spark - Replace first occurrence in a string-CodePudding

I want to use the replaceFirst() function in spark scala sql. or Is it possible to use the replaceFirst() function in spark scala dataframe?

Is this possible without using a UDF?

The function I want to do is:

println("abcdefgbchijkl".replaceFirst("bc","**BC**"))
// a**BC**defgbchijkl

However, the Column Type of DataFrame cannot be applied with Function:

var test0 = Seq("abcdefgbchijkl").toDF("col0")

test0
.select(col("col0").replaceFirst("bc","**BC**"))
.show(false)
/*
<console>:230: error: value replaceFirst is not a member of org.apache.spark.sql.Column
       .select(col("col0").replaceFirst("bc","**BC**"))
*/

Also, I don't know how to use it in SQL form:

%sql
-- How to use replaceFirst()
select replaceFirst()

CodePudding user response：

Replacing the first occurrence isn't something I can see supported out of the box by Spark, but it is possible by combining a few functions:

import org.apache.spark.sql.functions.{array_join, col, split}

val test0 = Seq("abcdefgbchijkl").toDF("col0") // replaced `var` with `val`

val stringToReplace = "bc"
val replacement = "**BC**"

test0
     // create a temporary column, splitting the string by the first occurrence of `bc`
    .withColumn("temp", split(col("col0"), stringToReplace, 2))
    // recombine the strings before and after `bc` with the desired replacement
    .withColumn("col0", array_join(col("temp"), replacement))
     // we no longer need this `temp` column
    .drop(col("temp"))

For (spark) SQL:

-- recombine the strings before and after `bc` with the desired replacement
SELECT tempr[0] || "**BC**" || tempr[1] AS col0
FROM (
  -- create a temporary column, splitting the string by the first occurrence of `bc`
  SELECT split(col0, "bc", 2) AS tempr
  FROM (
    SELECT 'abcdefgbchijkl' AS col0
  )
)