spark creates partition inside partition on S3

Question

I have below tab delimited sample dataset:

col1  period  col3  col4  col5  col6  col7  col8  col9  col10 col11 col12 col13 col14 col15 col16 col17 col18 col19 col20 col21 col22
ASSDF 202001  A B BFGF  SSDAA WDSF  SDSDSD  SDSDSSS SDSDSD  E F FS  E CURR1 CURR2 -99 CURR3 -99 -99 -99 -99
ASSDF 202002  A B BFGF  SSDAA WDSF  SDSDSD  SDSDSSS SDSDSD  E F FS  E CURR1 CURR2 -99 CURR3 -99 -99 -99 -99
ASSDF 202003  A B BFGF  SSDAA WDSF  SDSDSD  SDSDSSS SDSDSD  E F FS  E CURR1 CURR2 -99 CURR3 -99 -99 -99 -99
ASSDF 202004  A B BFGF  SSDAA WDSF  SDSDSD  SDSDSSS SDSDSD  E F FS  E CURR1 CURR2 -99 CURR3 -99 -99 -99 -99
...
...
ASSDF 202312  A B BFGF  SSDAA WDSF  SDSDSD  SDSDSSS SDSDSD  E F FS  E CURR1 CURR2 -99 CURR3 -99 -99 -99 -99

I am running some transformation on this data and final data is in spark dataset "DS1" . After that I am writing that dataset to s3 with "period" partition. Since I want period in s3 files as well, I am creating another column "datasetPeriod" from from period column.

My scala function to save TSV dataset.

def saveTsvDataset(dataframe: DataFrame, outputFullPath: String, numPartitions: Integer, partitionCols: String*): Unit = {
    dataframe
      .repartition(numPartitions)
      .write
      .partitionBy(partitionCols:_*)
      .mode(SaveMode.Overwrite)
      .option("sep", "\t")
      .csv(outputFullPath)
  }

Scala code to save dataset on s3. Adding new column datasetPeriod for partition on s3.

 saveTsvDataset(
      DS1.withColumn("datasetPeriod",$"period")
      , "s3://s3_path"
      , 100
      , "period"
    )

Now, my problem is I have period from 202001 to 202312 and when I am writing on s3 with partition on "datasetPeriod" sometimes it creates partition inside partition for any random period. So this happens randomly for any period. I never see this happened for multiple periods. It creates path like "s3://s3_path/datasetPeriod=202008/datasetPeriod=202008" .

Answer 1

You already have a period column in your DataFrame. So no need to create one more new duplicate datasetPeriod column.

When you write DataFrame to a s3://../parentFolder using .partitionBy("period") it creates folders like below:

df.write.partitionBy("period").csv("s3://../parentFolder/")
s3://.../parentFolder/period=202001/
s3://.../parentFolder/period=202002/
s3://.../parentFolder/period=202003/
...
s3://.../parentFolder/period=202312/

While reading the data back, just mention the path till parentFolder only, that will automatically read period as one of the columns.

val df = spark.read.csv("s3://../parentFolder/")
//df.schema will give you `period` as one of the column
df.printSchema
root
 |-- col1: string (nullable = true)
 |-- .... //other columns go here
 |-- period: string (nullable = true)

That being said, whatever multiple partition inside partition column you are getting are only due to the wrong path you are using while writing data using partitionBy.