Big Data: On RDDs, Dataframes,Hive QL with Pyspark and SparkR-Part 3

Posted on April 12, 2019 by Tinniam V Ganesh in R bloggers | 0 Comments

[This article was first published on R – Giga thoughts …, and kindly contributed to R-bloggers]. (You can report issue about the content on this page here)
Want to share your content on R-bloggers? click here if you have a blog, or here if you don't.

Some people, when confronted with a problem, think “I know, I’ll use regular expressions.” Now they have two problems. – Jamie Zawinski

Some programmers, when confronted with a problem, think “I know, I’ll use floating point arithmetic.” Now they have 1.999999999997 problems. – @tomscott

Some people, when confronted with a problem, think “I know, I’ll use multithreading”. Nothhw tpe yawrve o oblems. – @d6

Some people, when confronted with a problem, think “I know, I’ll use versioning.” Now they have 2.1.0 problems. – @JaesCoyle

Some people, when faced with a problem, think, “I know, I’ll use binary.” Now they have 10 problems. – @nedbat

Introduction

The power of Spark, which operates on in-memory datasets, is the fact that it stores the data as collections using Resilient Distributed Datasets (RDDs), which are themselves distributed in partitions across clusters. RDDs, are a fast way of processing data, as the data is operated on parallel based on the map-reduce paradigm. RDDs can be be used when the operations are low level. RDDs, are typically used on unstructured data like logs or text. For structured and semi-structured data, Spark has a higher abstraction called Dataframes. Handling data through dataframes are extremely fast as they are Optimized using the Catalyst Optimization engine and the performance is orders of magnitude faster than RDDs. In addition Dataframes also use Tungsten which handle memory management and garbage collection more effectively.

The picture below shows the performance improvement achieved with Dataframes over RDDs

Benefits from Project Tungsten

Npte: The above data and graph is taken from the course Big Data Analysis with Apache Spark at edX, UC Berkeley
This post is a continuation of my 2 earlier posts
1. Big Data-1: Move into the big league:Graduate from Python to Pyspark
2. Big Data-2: Move into the big league:Graduate from R to SparkR

In this post I perform equivalent operations on a small dataset using RDDs, Dataframes in Pyspark & SparkR and HiveQL. As in some of my earlier posts, I have used the tendulkar.csv file for this post. The dataset is small and allows me to do most everything from data cleaning, data transformation and grouping etc.
You can clone fork the notebooks from github at Big Data:Part 3

1. RDD – Select all columns of tables

from pyspark import SparkContext 
rdd = sc.textFile( "/FileStore/tables/tendulkar.csv")
rdd.map(lambda line: (line.split(","))).take(5)
Out[90]: [[‘Runs’, ‘Mins’, ‘BF’, ‘4s’, ‘6s’, ‘SR’, ‘Pos’, ‘Dismissal’, ‘Inns’, ‘Opposition’, ‘Ground’, ‘Start Date’], [’15’, ’28’, ’24’, ‘2’, ‘0’, ‘62.5’, ‘6’, ‘bowled’, ‘2’, ‘v Pakistan’, ‘Karachi’, ’15-Nov-89′], [‘DNB’, ‘-‘, ‘-‘, ‘-‘, ‘-‘, ‘-‘, ‘-‘, ‘-‘, ‘4’, ‘v Pakistan’, ‘Karachi’, ’15-Nov-89′], [’59’, ‘254’, ‘172’, ‘4’, ‘0’, ‘34.3’, ‘6’, ‘lbw’, ‘1’, ‘v Pakistan’, ‘Faisalabad’, ’23-Nov-89′], [‘8′, ’24’, ’16’, ‘1’, ‘0’, ’50’, ‘6’, ‘run out’, ‘3’, ‘v Pakistan’, ‘Faisalabad’, ’23-Nov-89′]]

1b.RDD – Select columns 1 to 4

from pyspark import SparkContext 
rdd = sc.textFile( "/FileStore/tables/tendulkar.csv")
rdd.map(lambda line: (line.split(",")[0:4])).take(5)

1c. RDD – Select specific columns 0, 10

from pyspark import SparkContext 
rdd = sc.textFile( "/FileStore/tables/tendulkar.csv")
df=rdd.map(lambda line: (line.split(",")))
df.map(lambda x: (x[10],x[0])).take(5)
Out[92]:
[(‘Ground’, ‘Runs’),
(‘Karachi’, ’15’),
(‘Karachi’, ‘DNB’),
(‘Faisalabad’, ’59’),
(‘Faisalabad’, ‘8’)]

2. Dataframe:Pyspark – Select all columns

from pyspark.sql import SparkSession
spark = SparkSession.builder.appName('Read CSV DF').getOrCreate()
tendulkar1 = spark.read.format('csv').option('header','true').load('/FileStore/tables/tendulkar.csv')
tendulkar1.show(5)

2a. Dataframe:Pyspark- Select specific columns

from pyspark.sql import SparkSession
spark = SparkSession.builder.appName('Read CSV DF').getOrCreate()
tendulkar1 = spark.read.format('csv').option('header','true').load('/FileStore/tables/tendulkar.csv')
tendulkar1.select("Runs","BF","Mins").show(5)
+—-+—+—-+
|Runs| BF|Mins|
+—-+—+—-+
| 15| 24| 28|
| DNB| -| -|
| 59|172| 254|
| 8| 16| 24|
| 41| 90| 124|
+—-+—+—-+

3. Dataframe:SparkR – Select all columns

# Load the SparkR library
library(SparkR)
# Initiate a SparkR session
sparkR.session()
tendulkar1 <- read.df("/FileStore/tables/tendulkar.csv", 
                header = "true", 
                delimiter = ",", 
                source = "csv", 
                inferSchema = "true", 
                na.strings = "")

# Check the dimensions of the dataframe
df=SparkR::select(tendulkar1,"*")
head(SparkR::collect(df))

  Runs Mins  BF 4s 6s    SR Pos Dismissal Inns Opposition     Ground Start Date
1   15   28  24  2  0  62.5   6    bowled    2 v Pakistan    Karachi  15-Nov-89
2  DNB    -   -  -  -     -   -         -    4 v Pakistan    Karachi  15-Nov-89
3   59  254 172  4  0  34.3   6       lbw    1 v Pakistan Faisalabad  23-Nov-89
4    8   24  16  1  0    50   6   run out    3 v Pakistan Faisalabad  23-Nov-89
5   41  124  90  5  0 45.55   7    bowled    1 v Pakistan     Lahore   1-Dec-89
6   35   74  51  5  0 68.62   6       lbw    1 v Pakistan    Sialkot   9-Dec-89

3a. Dataframe:SparkR- Select specific columns

# Load the SparkR library
library(SparkR)
# Initiate a SparkR session
sparkR.session()
tendulkar1 <- read.df("/FileStore/tables/tendulkar.csv", 
                header = "true", 
                delimiter = ",", 
                source = "csv", 
                inferSchema = "true", 
                na.strings = "")

# Check the dimensions of the dataframe
df=SparkR::select(tendulkar1, "Runs", "BF","Mins")
head(SparkR::collect(df))
Runs BF Mins
1 15 24 28
2 DNB – –
3 59 172 254
4 8 16 24
5 41 90 124
6 35 51 74

4. Hive QL – Select all columns

from pyspark.sql import SparkSession
spark = SparkSession.builder.appName('Read CSV DF').getOrCreate()
tendulkar1 = spark.read.format('csv').option('header','true').load('/FileStore/tables/tendulkar.csv')
tendulkar1.createOrReplaceTempView('tendulkar1_table')
spark.sql('select  * from tendulkar1_table limit 5').show(10, truncate = False)
+—-+—+—-++—-+—-+—+—+—+—–+—+———+—-+———-+———-+———-+
|Runs|Mins|BF |4s |6s |SR |Pos|Dismissal|Inns|Opposition|Ground |Start Date|
+—-+—-+—+—+—+—–+—+———+—-+———-+———-+———-+
|15 |28 |24 |2 |0 |62.5 |6 |bowled |2 |v Pakistan|Karachi |15-Nov-89 |
|DNB |- |- |- |- |- |- |- |4 |v Pakistan|Karachi |15-Nov-89 |
|59 |254 |172|4 |0 |34.3 |6 |lbw |1 |v Pakistan|Faisalabad|23-Nov-89 |
|8 |24 |16 |1 |0 |50 |6 |run out |3 |v Pakistan|Faisalabad|23-Nov-89 |
|41 |124 |90 |5 |0 |45.55|7 |bowled |1 |v Pakistan|Lahore |1-Dec-89 |
+—-+—-+—+—+—+—–+—+———+—-+———-+———-+———-+

4a. Hive QL – Select specific columns

from pyspark.sql import SparkSession
spark = SparkSession.builder.appName('Read CSV DF').getOrCreate()
tendulkar1 = spark.read.format('csv').option('header','true').load('/FileStore/tables/tendulkar.csv')
tendulkar1.createOrReplaceTempView('tendulkar1_table')
spark.sql('select  Runs, BF,Mins from tendulkar1_table limit 5').show(10, truncate = False)
|Runs|BF |Mins|
+—-+—+—-+
|15 |24 |28 |
|DNB |- |- |
|59 |172|254 |
|8 |16 |24 |
|41 |90 |124 |
+—-+—+—-+

5. RDD – Filter rows on specific condition

from pyspark import SparkContext
rdd = sc.textFile( "/FileStore/tables/tendulkar.csv")
df=(rdd.map(lambda line: line.split(",")[:])
      .filter(lambda x: x !="DNB")
      .filter(lambda x: x!= "TDNB")
      .filter(lambda x: x!="absent")
      .map(lambda x: [x[0].replace("*","")] + x[1:]))

df.take(5)

5a. Dataframe:Pyspark – Filter rows on specific condition

from pyspark.sql import SparkSession
from pyspark.sql.functions import regexp_replace
spark = SparkSession.builder.appName('Read CSV DF').getOrCreate()
tendulkar1 = spark.read.format('csv').option('header','true').load('/FileStore/tables/tendulkar.csv')
tendulkar1= tendulkar1.where(tendulkar1['Runs'] != 'DNB')
tendulkar1= tendulkar1.where(tendulkar1['Runs'] != 'TDNB')
tendulkar1= tendulkar1.where(tendulkar1['Runs'] != 'absent')
tendulkar1 = tendulkar1.withColumn('Runs', regexp_replace('Runs', '[*]', ''))
tendulkar1.show(5)
+—-+—-+—+—+—+—–+—+———+—-+———-+———-+———-+
|Runs|Mins| BF| 4s| 6s| SR|Pos|Dismissal|Inns|Opposition| Ground|Start Date|
+—-+—-+—+—+—+—–+—+———+—-+———-+———-+———-+
| 15| 28| 24| 2| 0| 62.5| 6| bowled| 2|v Pakistan| Karachi| 15-Nov-89|
| 59| 254|172| 4| 0| 34.3| 6| lbw| 1|v Pakistan|Faisalabad| 23-Nov-89|
| 8| 24| 16| 1| 0| 50| 6| run out| 3|v Pakistan|Faisalabad| 23-Nov-89|
| 41| 124| 90| 5| 0|45.55| 7| bowled| 1|v Pakistan| Lahore| 1-Dec-89|
| 35| 74| 51| 5| 0|68.62| 6| lbw| 1|v Pakistan| Sialkot| 9-Dec-89|
+—-+—-+—+—+—+—–+—+———+—-+———-+———-+———-+
only showing top 5 rows

5b. Dataframe:SparkR – Filter rows on specific condition

sparkR.session()

tendulkar1 <- read.df("/FileStore/tables/tendulkar.csv", 
                header = "true", 
                delimiter = ",", 
                source = "csv", 
                inferSchema = "true", 
                na.strings = "")

print(dim(tendulkar1))
tendulkar1 <-SparkR::filter(tendulkar1,tendulkar1$Runs != "DNB")
print(dim(tendulkar1))
tendulkar1<-SparkR::filter(tendulkar1,tendulkar1$Runs != "TDNB")
print(dim(tendulkar1))
tendulkar1<-SparkR::filter(tendulkar1,tendulkar1$Runs != "absent")
print(dim(tendulkar1))

# Cast the string type Runs to double
withColumn(tendulkar1, "Runs", cast(tendulkar1$Runs, "double"))
head(SparkR::distinct(tendulkar1[,"Runs"]),20)
# Remove the "* indicating not out
tendulkar1$Runs=SparkR::regexp_replace(tendulkar1$Runs, "\\*", "")
df=SparkR::select(tendulkar1,"*")
head(SparkR::collect(df))

5c Hive QL – Filter rows on specific condition

from pyspark.sql import SparkSession
spark = SparkSession.builder.appName('Read CSV DF').getOrCreate()
tendulkar1 = spark.read.format('csv').option('header','true').load('/FileStore/tables/tendulkar.csv')
tendulkar1.createOrReplaceTempView('tendulkar1_table')
spark.sql('select  Runs, BF,Mins from tendulkar1_table where Runs NOT IN  ("DNB","TDNB","absent")').show(10, truncate = False)
+—-+—+—-+
|Runs|BF |Mins|
+—-+—+—-+
|15 |24 |28 |
|59 |172|254 |
|8 |16 |24 |
|41 |90 |124 |
|35 |51 |74 |
|57 |134|193 |
|0 |1 |1 |
|24 |44 |50 |
|88 |266|324 |
|5 |13 |15 |
+—-+—+—-+
only showing top 10 rows

6. RDD – Find rows where Runs > 50

from pyspark import SparkContext
rdd = sc.textFile( "/FileStore/tables/tendulkar.csv")
df=rdd.map(lambda line: (line.split(",")))
df=rdd.map(lambda line: line.split(",")[0:4]) \
   .filter(lambda x: x[0] not in ["DNB", "TDNB", "absent"])
df1=df.map(lambda x: [x[0].replace("*","")] + x[1:4])
header=df1.first()
df2=df1.filter(lambda x: x !=header)
df3=df2.map(lambda x: [float(x[0])] +x[1:4])
df3.filter(lambda x: x[0]>=50).take(10)
Out[101]: 
[[59.0, '254', '172', '4'],
 [57.0, '193', '134', '6'],
 [88.0, '324', '266', '5'],
 [68.0, '216', '136', '8'],
 [119.0, '225', '189', '17'],
 [148.0, '298', '213', '14'],
 [114.0, '228', '161', '16'],
 [111.0, '373', '270', '19'],
 [73.0, '272', '208', '8'],
 [50.0, '158', '118', '6']]

6a. Dataframe:Pyspark – Find rows where Runs >50

from pyspark.sql import SparkSession

from pyspark.sql.functions import regexp_replace
from pyspark.sql.types import IntegerType
spark = SparkSession.builder.appName('Read CSV DF').getOrCreate()
tendulkar1 = spark.read.format('csv').option('header','true').load('/FileStore/tables/tendulkar.csv')
tendulkar1= tendulkar1.where(tendulkar1['Runs'] != 'DNB')
tendulkar1= tendulkar1.where(tendulkar1['Runs'] != 'TDNB')
tendulkar1= tendulkar1.where(tendulkar1['Runs'] != 'absent')
tendulkar1 = tendulkar1.withColumn("Runs", tendulkar1["Runs"].cast(IntegerType()))
tendulkar1.filter(tendulkar1['Runs']>=50).show(10)
+—-+—-+—+—+—+—–+—+———+—-+————–+————+———-+
|Runs|Mins| BF| 4s| 6s| SR|Pos|Dismissal|Inns| Opposition| Ground|Start Date|
+—-+—-+—+—+—+—–+—+———+—-+————–+————+———-+
| 59| 254|172| 4| 0| 34.3| 6| lbw| 1| v Pakistan| Faisalabad| 23-Nov-89|
| 57| 193|134| 6| 0|42.53| 6| caught| 3| v Pakistan| Sialkot| 9-Dec-89|
| 88| 324|266| 5| 0|33.08| 6| caught| 1| v New Zealand| Napier| 9-Feb-90|
| 68| 216|136| 8| 0| 50| 6| caught| 2| v England| Manchester| 9-Aug-90|
| 114| 228|161| 16| 0| 70.8| 4| caught| 2| v Australia| Perth| 1-Feb-92|
| 111| 373|270| 19| 0|41.11| 4| caught| 2|v South Africa|Johannesburg| 26-Nov-92|
| 73| 272|208| 8| 1|35.09| 5| caught| 2|v South Africa| Cape Town| 2-Jan-93|
| 50| 158|118| 6| 0|42.37| 4| caught| 1| v England| Kolkata| 29-Jan-93|
| 165| 361|296| 24| 1|55.74| 4| caught| 1| v England| Chennai| 11-Feb-93|
| 78| 285|213| 10| 0|36.61| 4| lbw| 2| v England| Mumbai| 19-Feb-93|
+—-+—-+—+—+—+—–+—+———+—-+————–+————+———-+

6b. Dataframe:SparkR – Find rows where Runs >50

# Load the SparkR library
library(SparkR)
sparkR.session()

tendulkar1 <- read.df("/FileStore/tables/tendulkar.csv", 
                header = "true", 
                delimiter = ",", 
                source = "csv", 
                inferSchema = "true", 
                na.strings = "")

print(dim(tendulkar1))
tendulkar1 <-SparkR::filter(tendulkar1,tendulkar1$Runs != "DNB")
print(dim(tendulkar1))
tendulkar1<-SparkR::filter(tendulkar1,tendulkar1$Runs != "TDNB")
print(dim(tendulkar1))
tendulkar1<-SparkR::filter(tendulkar1,tendulkar1$Runs != "absent")
print(dim(tendulkar1))

# Cast the string type Runs to double
withColumn(tendulkar1, "Runs", cast(tendulkar1$Runs, "double"))
head(SparkR::distinct(tendulkar1[,"Runs"]),20)
# Remove the "* indicating not out
tendulkar1$Runs=SparkR::regexp_replace(tendulkar1$Runs, "\\*", "")
df=SparkR::select(tendulkar1,"*")
df=SparkR::filter(tendulkar1, tendulkar1$Runs > 50)
head(SparkR::collect(df))
  Runs Mins  BF 4s 6s    SR Pos Dismissal Inns    Opposition     Ground
1   59  254 172  4  0  34.3   6       lbw    1    v Pakistan Faisalabad
2   57  193 134  6  0 42.53   6    caught    3    v Pakistan    Sialkot
3   88  324 266  5  0 33.08   6    caught    1 v New Zealand     Napier
4   68  216 136  8  0    50   6    caught    2     v England Manchester
5  119  225 189 17  0 62.96   6   not out    4     v England Manchester
6  148  298 213 14  0 69.48   6   not out    2   v Australia     Sydney
  Start Date
1  23-Nov-89
2   9-Dec-89
3   9-Feb-90
4   9-Aug-90
5   9-Aug-90
6   2-Jan-92

 

7 RDD – groupByKey() and reduceByKey()

from pyspark import SparkContext
from pyspark.mllib.stat import Statistics
rdd = sc.textFile( "/FileStore/tables/tendulkar.csv")
df=rdd.map(lambda line: (line.split(",")))
df=rdd.map(lambda line: line.split(",")[0:]) \
   .filter(lambda x: x[0] not in ["DNB", "TDNB", "absent"])
df1=df.map(lambda x: [x[0].replace("*","")] + x[1:])
header=df1.first()
df2=df1.filter(lambda x: x !=header)
df3=df2.map(lambda x: [float(x[0])] +x[1:])
df4 = df3.map(lambda x: (x[10],x[0]))
df5=df4.reduceByKey(lambda a,b: a+b,1)
df4.groupByKey().mapValues(lambda x: sum(x) / len(x)).take(10)

7a Dataframe:Pyspark – Compute mean, min and max

from pyspark.sql.functions import *
tendulkar1= (sqlContext
         .read.format("com.databricks.spark.csv")
         .options(delimiter=',', header='true', inferschema='true')
         .load("/FileStore/tables/tendulkar.csv"))
tendulkar1= tendulkar1.where(tendulkar1['Runs'] != 'DNB')
tendulkar1= tendulkar1.where(tendulkar1['Runs'] != 'TDNB')
tendulkar1 = tendulkar1.withColumn('Runs', regexp_replace('Runs', '[*]', ''))
tendulkar1.select('Runs').rdd.distinct().collect()

from pyspark.sql import functions as F
df=tendulkar1[['Runs','BF','Ground']].groupby(tendulkar1['Ground']).agg(F.mean(tendulkar1['Runs']),F.min(tendulkar1['Runs']),F.max(tendulkar1['Runs']))
df.show()

7b Dataframe:SparkR – Compute mean, min and max

sparkR.session()

tendulkar1 <- read.df("/FileStore/tables/tendulkar.csv", 
                header = "true", 
                delimiter = ",", 
                source = "csv", 
                inferSchema = "true", 
                na.strings = "")

print(dim(tendulkar1))
tendulkar1 <-SparkR::filter(tendulkar1,tendulkar1$Runs != "DNB")
print(dim(tendulkar1))
tendulkar1<-SparkR::filter(tendulkar1,tendulkar1$Runs != "TDNB")
print(dim(tendulkar1))
tendulkar1<-SparkR::filter(tendulkar1,tendulkar1$Runs != "absent")
print(dim(tendulkar1))

# Cast the string type Runs to double
withColumn(tendulkar1, "Runs", cast(tendulkar1$Runs, "double"))
head(SparkR::distinct(tendulkar1[,"Runs"]),20)
# Remove the "* indicating not out
tendulkar1$Runs=SparkR::regexp_replace(tendulkar1$Runs, "\\*", "")
head(SparkR::distinct(tendulkar1[,"Runs"]),20)
df=SparkR::summarize(SparkR::groupBy(tendulkar1, tendulkar1$Ground), mean = mean(tendulkar1$Runs), minRuns=min(tendulkar1$Runs),maxRuns=max(tendulkar1$Runs))
head(df,20)
          Ground       mean minRuns maxRuns
1      Bangalore  54.312500       0      96
2       Adelaide  32.600000       0      61
3  Colombo (PSS)  37.200000      14      71
4   Christchurch  12.000000       0      24
5       Auckland   5.000000       5       5
6        Chennai  60.625000       0      81
7      Centurion  73.500000     111      36
8       Brisbane   7.666667       0       7
9     Birmingham  46.750000       1      40
10     Ahmedabad  40.125000     100       8
11 Colombo (RPS) 143.000000     143     143
12    Chittagong  57.800000     101      36
13     Cape Town  69.857143      14       9
14    Bridgetown  26.000000       0      92
15      Bulawayo  55.000000      36      74
16         Delhi  39.947368       0      76
17    Chandigarh  11.000000      11      11
18  Bloemfontein  85.000000      15     155
19 Colombo (SSC)  77.555556     104       8
20       Cuttack   2.000000       2       2

Also see
1. My book ‘Practical Machine Learning in R and Python: Third edition’ on Amazon
2.My book ‘Deep Learning from first principles:Second Edition’ now on Amazon
3.The Clash of the Titans in Test and ODI cricket
4. Introducing QCSimulator: A 5-qubit quantum computing simulator in R
5.Latency, throughput implications for the Cloud
6. Simulating a Web Joint in Android
5. Pitching yorkpy … short of good length to IPL – Part 1

To see all posts click Index of Posts

To leave a comment for the author, please follow the link and comment on their blog: R – Giga thoughts ….
R-bloggers.com offers daily e-mail updates about R news and tutorials about learning R and many other topics. Click here if you're looking to post or find an R/data-science job.
Want to share your content on R-bloggers? click here if you have a blog, or here if you don't.

Copyright © 2022 | MH Corporate basic by MH Themes

Never miss an update!
Subscribe to R-bloggers to receive
e-mails with the latest R posts.
(You will not see this message again.)

Click here to close (This popup will not appear again)