# Learning Goal: I’m working on a databases exercise and need an explanation and a

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How many distinct drives (by model+serial) are installed (i.e., that exist in the data) in each year?
What’s the max drive capacity per year?
Full dataset: change the file path to: file:///ssd/data/backblaze.csv (146 million rows) – my solution took 17minRun spark like this: spark-submit backblaze-spark.py –master=local[5]Or to hide log messages: spark-submit backblaze-spark.py –master=local[5] 2> /dev/nullStarting code with some examples that you can remove:from pyspark.sql import SparkSessionspark = SparkSession.builder.appName(“Backblaze”).getOrCreate()schema = “day DATE, serial STRING, model STRING, capacity LONG, failure INTEGER”d = spark.read.schema(schema).load(“file:///home/jeckroth/cinf201/spark/assignment/small-backblaze.csv”, format=”csv”, sep=”,”, header=”true”)d = d.rdd# print first 10 rowsprint(d.take(10))## How many failures occurred each year?# make key (year) & value (failure 0/1)d2 = d.map(lambda row: (row.day.year, row.failure))# add up failures per yearfailureCounts = d2.reduceByKey(lambda cnt, rowcnt: cnt + rowcnt)print(failureCounts.collect())## Which model (not serial number) has the most failures overall?# grab model & failure from data, model is the keyd3 = d.map(lambda row: (row.model, row.failure))# count failures for that model; result so far: [(modelX, 55), (modelY, 2100)]d3 = d3.reduceByKey(lambda cnt, rowcnt: cnt + rowcnt)# flip keys and values; result so far: [(55, modelX), (2100, modelY)]d3 = d3.map(lambda pair: (pair[1], pair[0]))# sort by value (second in the pair)d3 = d3.sortByKey(ascending=False) ### NOT EFFICIENT TECHNIQUEprint(d3.collect())

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