Pig Latin basics in Hadoop - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to load data from a file named 'data.txt'.

Hadoop

data = LOAD 'data.txt' USING [1];

Drag options to blanks, or click blank then click option'

APigStorage()

BTextLoader()

CCsvLoader()

DJsonLoader()

Attempts:

3 left

💡 Hint

Common Mistakes

Using JsonLoader() for plain text files.

Forgetting to specify a loader.

Using CsvLoader() when the file is not CSV.

PigStorage() is the default loader in Pig Latin for loading plain text files with fields separated by tabs.

2fill in blank

medium

Complete the code to filter records where the age field is greater than 30.

Hadoop

filtered_data = FILTER data BY [1] > 30;

Drag options to blanks, or click blank then click option'

Adata

B30

Cage

Dcount

Attempts:

3 left

💡 Hint

Common Mistakes

Using the dataset name instead of the field name.

Using a number instead of a field name.

Using a field that does not exist.

The FILTER statement uses the field name 'age' to compare values greater than 30.

3fill in blank

hard

Fix the error in the code to group data by the 'department' field.

Hadoop

grouped = GROUP data BY [1];

Drag options to blanks, or click blank then click option'

Aage

Bdepartment

Cname

Dsalary

Attempts:

3 left

💡 Hint

Common Mistakes

Grouping by a field that is not categorical.

Using a field that does not exist in the data.

Using the dataset name instead of a field.

Grouping is done by the 'department' field to aggregate data per department.

4fill in blank

hard

Fill both blanks to create a new relation with only the 'name' and 'salary' fields.

Hadoop

selected = FOREACH data GENERATE [1], [2];

Drag options to blanks, or click blank then click option'

Aname

Bage

Csalary

Ddepartment

Attempts:

3 left

💡 Hint

Common Mistakes

Selecting fields not present in the data.

Selecting fields unrelated to the task.

Mixing up field names.

The FOREACH GENERATE statement selects the 'name' and 'salary' fields from the data.

5fill in blank

hard

Fill all three blanks to calculate the average salary per department.

Hadoop

grouped = GROUP data BY [1];
avg_salary = FOREACH grouped GENERATE [2], AVG([3]);

Drag options to blanks, or click blank then click option'

Adepartment

Bgroup

Cdata.salary

Dsalary

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'salary' instead of 'data.salary' inside AVG.

Not using 'group' to output the group key.

Grouping by the wrong field.

First, group by 'department'. Then generate the group name and average of the salary field from the grouped data.

Practice

1. What is the main purpose of the FILTER statement in Pig Latin?

easy

A. To select rows that meet a condition

B. To combine two datasets

C. To load data from a file

D. To save the results to storage

Solution

1. Step 1: Understand the role of FILTER

   The FILTER statement is used to keep only the rows that satisfy a given condition.

2. Step 2: Compare with other statements

   LOAD reads data, GROUP groups data, STORE saves data, so FILTER is for selecting rows.

3. Final Answer:

   To select rows that meet a condition -> Option A

4. Quick Check:

   FILTER = select rows [OK]

Hint: FILTER keeps rows matching condition, like a sieve [OK]

Common Mistakes:

• Confusing FILTER with GROUP
• Thinking FILTER saves data
• Mixing FILTER with LOAD

2. Which of the following is the correct syntax to load a file named data.txt in Pig Latin?

easy

A. LOAD 'data.txt' USING PigStorage();

B. LOAD data.txt USING PigStorage();

C. LOAD 'data.txt' AS PigStorage();

D. LOAD 'data.txt' USING PigStorage

Solution

1. Step 1: Check the LOAD syntax

   LOAD requires the file path as a string in quotes and the loader function with parentheses.

2. Step 2: Validate each option

   LOAD 'data.txt' USING PigStorage(); uses quotes and parentheses correctly. LOAD data.txt USING PigStorage(); misses quotes. LOAD 'data.txt' AS PigStorage(); uses AS instead of USING. LOAD 'data.txt' USING PigStorage misses parentheses.

3. Final Answer:

   LOAD 'data.txt' USING PigStorage(); -> Option A

4. Quick Check:

   LOAD 'file' USING loader(); [OK]

Hint: LOAD needs quotes and parentheses for loader [OK]

Common Mistakes:

• Forgetting quotes around filename
• Using AS instead of USING
• Omitting parentheses after loader

3. Given the following Pig Latin code:

A = LOAD 'numbers.txt' USING PigStorage(',');
B = FILTER A BY $0 > 10;
C = FOREACH B GENERATE $0;
DUMP C;

What will be the output if numbers.txt contains:
5,abc
15,def
8,ghi
20,jkl

medium

A. (5,abc)
(8,ghi)

B. (5)
(8)

C. (15,def)
(20,jkl)

D. (15)
(20)

Solution

1. Step 1: Understand the FILTER condition

   FILTER keeps rows where first column ($0) is greater than 10, so rows with 15 and 20 remain.

2. Step 2: Understand FOREACH GENERATE

   FOREACH selects only the first column ($0), so output shows only 15 and 20 as single values.

3. Final Answer:

   (15) (20) -> Option D

4. Quick Check:

   FILTER $0 > 10 then select $0 [OK]

Hint: FILTER then FOREACH select column shows filtered values [OK]

Common Mistakes:

• Including second column in output
• Selecting rows less than or equal to 10
• Confusing FILTER condition

4. Identify the error in this Pig Latin script:

data = LOAD 'input.txt' USING PigStorage(',');
filtered = FILTER data BY $1 == 'USA';
grouped = GROUP filtered BY $2;
result = FOREACH grouped GENERATE group, COUNT(filtered);
STORE result INTO 'output';

medium

A. COUNT should use filtered instead of group

B. STORE command missing USING clause

C. FILTER condition uses wrong column index

D. GROUP should use filtered instead of data

Solution

1. Step 1: Check STORE syntax

   STORE requires a USING clause to specify the storage format, e.g., PigStorage().

2. Step 2: Verify other statements

   GROUP uses filtered correctly, COUNT uses filtered correctly, FILTER condition is valid if $1 is country column.

3. Final Answer:

   STORE command missing USING clause -> Option B

4. Quick Check:

   STORE ... INTO 'path' USING loader() [OK]

Hint: STORE needs USING clause to save data [OK]

Common Mistakes:

• Omitting USING in STORE
• Confusing GROUP input
• Misunderstanding COUNT argument

5. You have a dataset of sales with columns: product_id, region, amount. You want to find total sales per region but only for sales above 100. Which Pig Latin sequence correctly achieves this?

hard

A. A = LOAD 'sales.txt' USING PigStorage(',');
B = FILTER A BY amount > 100;
C = GROUP B BY region;
D = FOREACH C GENERATE group, SUM(B.amount);
STORE D INTO 'result' USING PigStorage();

B. A = LOAD 'sales.txt' USING PigStorage(',');
B = FILTER A BY $2 > 100;
C = GROUP B BY $1;
D = FOREACH C GENERATE group, SUM(B.$2);
STORE D INTO 'result';

C. A = LOAD 'sales.txt' USING PigStorage(',');
B = FILTER A BY $2 > 100;
C = GROUP B BY $1;
D = FOREACH C GENERATE group, SUM(B.$2);
STORE D INTO 'result' USING PigStorage();

D. A = LOAD 'sales.txt' USING PigStorage(',');
B = FILTER A BY $1 > 100;
C = GROUP B BY $2;
D = FOREACH C GENERATE group, SUM(B.$3);
STORE D INTO 'result' USING PigStorage();

Solution

1. Step 1: Identify correct column indexes

   Columns: product_id ($0), region ($1), amount ($2). Filter by amount > 100 means FILTER BY $2 > 100.

2. Step 2: Group by region and sum amount

   Group by $1 (region), then sum B.$2 (amount) in FOREACH. STORE needs USING clause.

3. Step 3: Check each option

   A = LOAD 'sales.txt' USING PigStorage(','); B = FILTER A BY $2 > 100; C = GROUP B BY $1; D = FOREACH C GENERATE group, SUM(B.$2); STORE D INTO 'result' USING PigStorage(); matches all requirements: correct filter, group, sum, and STORE syntax.

4. Final Answer:

   Option C code sequence -> Option C

5. Quick Check:

   Filter $2>100, group $1, sum $2, STORE with USING [OK]

Hint: Use correct column indexes and STORE with USING [OK]

Common Mistakes:

• Using wrong column indexes for filter or group
• Omitting USING in STORE
• Summing wrong column