PySpark - Sum a column in dataframe and return results as int

Question

I have a pyspark dataframe with a column of numbers. I need to sum that column and then have the result return as an int in a python variable.

df = spark.cr         


        

Answer 1

The simplest way really :

df.groupBy().sum().collect()

But it is very slow operation: Avoid groupByKey, you should use RDD and reduceByKey:

df.rdd.map(lambda x: (1,x[1])).reduceByKey(lambda x,y: x + y).collect()[0][1]

I tried on a bigger dataset and i measured the processing time:

RDD and ReduceByKey : 2.23 s

GroupByKey: 30.5 s