DataFrame simple aggregation performance benchmark

df.py

data = sqlContext.load("/home/rxin/ints.parquet")
data.groupBy("a").agg(col("a"), avg("num")).collect()

df.scala

val data = sqlContext.load("/home/rxin/ints.parquet")
data.groupBy("a").agg(col("a"), avg("num")).collect()

generatedata.py

import random
from pyspark.sql import Row

data = sc.parallelize(xrange(1000)).flatMap(lambda x: [Row(a=random.randint(1, 10), num=random.randint(1, 100), str=("a" * random.randint(1, 30))) for i in xrange(10000)])
dataTable = sqlContext.createDataFrame(data)
dataTable.saveAsParquetFile("/home/rxin/ints.parquet")

rdd.py

pdata = sqlContext.load("/home/rxin/ints.parquet").select("a", "num")

sum_count = (
  pdata.map(lambda x: (x.a, [x.num, 1]))
    .reduceByKey(lambda x, y:
		  [x[0] + y[0], x[1] + y[1]])
    .collect())
[(x[0], float(x[1][0]) / x[1][1]) for x in sum_count]

rdd.scala

val pdata = sqlContext.load("/home/rxin/ints.parquet").select("a", "num")

val sum_count = pdata.map { row => (row.getInt(0), (row.getInt(1), 1)) }
  .reduceByKey { (a, b) =>
    (a._1 + b._1, a._2 + b._2)
  }.collect()

sum_count.foreach { case (a, (sum, count)) => println(s"$a: ${sum/count}") }

@melrief

// is it always better to use DataFrames instead of the functional API? //

No, it depends on the application. DataFrames are great for interactive analysis and BAU BI, but when writing my own machine learning algorithms or building complex applications I stick to the functional API.

// the reason why the DataFrame implementation is faster is only because of the Catalyst optimizer? //

No, I imagine it also uses mutable integers under the hood, whereas the Scala version uses tuple copying.

// Would it be possible to bring this optimization also to the functional API? //

Yes and no, yes in that the user could use something slightly lower level, like combineByKey or mapPartitions to pre-aggregate mutably at the partition level first. No in that it would be impossible for the Spark API to automagically do this.

Here you can find some analysis of this benchmark and its code: http://0x0fff.com/spark-dataframes-are-faster-arent-they/

it is confusing , since in data science machine learning we need real life algorithms comparison. Take random forest from sci kit learn (not from spark ML very poor library) or deep neural network and run.