How to skip first and last line from a dat file and make it to dataframe using scala in databricks

问题

H|*|D|*|PA|*|BJ|*|S|*|2019.05.27 08:54:24|##|
H|*|AP_ATTR_ID|*|AP_ID|*|OPER_ID|*|ATTR_ID|*|ATTR_GROUP|*|LST_UPD_USR|*|LST_UPD_TSTMP|##|
779045|*|Sar|*|SUPERVISOR HIERARCHY|*|Supervisor|*|2|*|128|*|2019.05.14 16:48:16|##|
779048|*|KK|*|SUPERVISOR HIERARCHY|*|Supervisor|*|2|*|116|*|2019.05.14 16:59:02|##|
779054|*|Nisha - A|*|EXACT|*|CustomColumnRow120|*|2|*|1165|*|2019.05.15 12:11:48|##|
T|*||*|2019.05.27 08:54:28|##|

file name is PA.dat.

I need to skip first line and also last line of the file.second line of the file is column name. Now I need to make a dataframe with columnanme and skipping those two line using scala.

N.B - need to skip that 'H' from second line also as it is not part of column name.

Please help me on this.

回答1:

Something like that. I don't know if sql.functions could split array into columns, so i did it using rdd.

import java.util.regex.Pattern
import org.apache.spark.sql.RowFactory
import org.apache.spark.sql.types.{StringType, StructField, StructType}
import org.apache.spark.sql.functions._ 

val data = spark.read
  .text("data/PA.dat")
  .toDF("val")
  .withColumn("id", monotonically_increasing_id())

val count = data.count()
val header = data.where('id === 1).collect().map(s => s.getString(0)).apply(0)
val columns = header
  .replace("H|*|", "")
  .replace("|##|", "")
  .replace("|*|", ",")
  .split(",")
val columnDelimiter = Pattern.quote("|*|")
val correctData = data.where('id > 1 && 'id < count - 1)
  .select(regexp_replace('val, columnDelimiter, ",").as("val"))
val splitIntoCols = correctData.rdd.map(s=>{
  val arr = s.getString(0).split(",")
  RowFactory.create(arr:_*)
})
val struct = StructType(columns.map(s=>StructField(s, StringType, true)))
val finalDF = spark.createDataFrame(splitIntoCols,struct)

finalDF.show()


+----------+---------+--------------------+------------------+----------+-----------+--------------------+
|AP_ATTR_ID|    AP_ID|             OPER_ID|           ATTR_ID|ATTR_GROUP|LST_UPD_USR|       LST_UPD_TSTMP|
+----------+---------+--------------------+------------------+----------+-----------+--------------------+
|    779045|      Sar|SUPERVISOR HIERARCHY|        Supervisor|         2|        128|2019.05.14 16:48:...|
|    779048|       KK|SUPERVISOR HIERARCHY|        Supervisor|         2|        116|2019.05.14 16:59:...|
|    779054|Nisha - A|               EXACT|CustomColumnRow120|         2|       1165|2019.05.15 12:11:...|
+----------+---------+--------------------+------------------+----------+-----------+--------------------+

来源：https://stackoverflow.com/questions/57987228/how-to-skip-first-and-last-line-from-a-dat-file-and-make-it-to-dataframe-using-s

标签

scala

apache-spark

apache-spark-sql

azure-databricks