CRUD operations in HBase in Hadoop - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a new HBase table named 'students'.

Hadoop

create '[1]', 'info'

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

Ateachers

Bclasses

Cstudents

Dsubjects

Attempts:

3 left

💡 Hint

Common Mistakes

Using a wrong table name like 'teachers' or 'classes'.

Omitting the column family name.

The create command followed by the table name and column family creates a new table. Here, 'students' is the correct table name.

2fill in blank

medium

Complete the code to insert a value 'John' into the 'name' column of the 'info' column family for row 'row1' in the 'students' table.

Hadoop

put 'students', 'row1', 'info:[1]', 'John'

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

Aaddress

Bage

Cgrade

Dname

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong column qualifier like 'age' or 'grade'.

Mixing up column family and column qualifier.

The column qualifier is 'name' inside the 'info' column family where the value 'John' is inserted.

3fill in blank

hard

Fix the error in the code to retrieve the value of the 'name' column from the 'info' column family for row 'row1' in the 'students' table.

Hadoop

get 'students', 'row1', '[1]'

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

Ainfo:name

Binfo-name

Cinfo_name

Dname:info

Attempts:

3 left

💡 Hint

Common Mistakes

Using a dash '-' or underscore '_' instead of colon ':'.

Reversing the order of column family and column.

The correct syntax to specify a column is 'column_family:column', so 'info:name' is correct.

4fill in blank

hard

Fill both blanks to delete the 'age' column from the 'info' column family for row 'row2' in the 'students' table.

Hadoop

delete 'students', '[1]', '[2]'

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

Arow2

Brow1

Cinfo:age

Dinfo:name

Attempts:

3 left

💡 Hint

Common Mistakes

Deleting the wrong row or column.

Using incorrect column format like 'info-name'.

The row key is 'row2' and the column to delete is 'info:age'.

5fill in blank

hard

Fill all three blanks to create a dictionary of all 'name' values from the 'info' column family for rows in the list ['row1', 'row2', 'row3'].

Hadoop

names = { [1]: get('students', [2], '[3]').value for [1] in ['row1', 'row2', 'row3'] }

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

Arow

B'name'

Cinfo:name

D'row'

Attempts:

3 left

💡 Hint

Common Mistakes

Using different variable names in the loop and get function.

Incorrect column name format.

The variable 'row' is used to iterate over the list of rows. The get command fetches the 'info:name' column value for each row.

Practice

1. Which HBase operation is used to retrieve data from a table?

easy

A. Get

B. Put

C. Delete

D. Scan

Solution

1. Step 1: Understand HBase CRUD operations

   HBase uses Get to read data, Put to create or update, Delete to remove, and Scan to read multiple rows.

2. Step 2: Identify the read operation

   Get is the specific operation to retrieve data for a single row.

3. Final Answer:

   Get -> Option A

4. Quick Check:

   Read = Get [OK]

Hint: Remember: Get = Read, Put = Create/Update [OK]

Common Mistakes:

• Confusing Put with Get
• Using Delete to read data
• Thinking Scan is for single row read

2. Which of the following is the correct syntax to insert data into HBase using Java API?

easy

A. Delete delete = new Delete(Bytes.toBytes("row1")); table.put(delete);

B. Get get = new Get(Bytes.toBytes("row1")); table.put(get);

C. Put put = new Put(Bytes.toBytes("row1")); put.addColumn(Bytes.toBytes("cf"), Bytes.toBytes("qual"), Bytes.toBytes("value")); table.put(put);

D. Put put = new Put("row1"); put.add("cf", "qual", "value"); table.get(put);

Solution

1. Step 1: Review correct Put syntax in HBase Java API

   Put requires a row key as bytes, then addColumn with column family, qualifier, and value as bytes, then call table.put(put).

2. Step 2: Check each option

   Put put = new Put(Bytes.toBytes("row1")); put.addColumn(Bytes.toBytes("cf"), Bytes.toBytes("qual"), Bytes.toBytes("value")); table.put(put); matches correct syntax. Get get = new Get(Bytes.toBytes("row1")); table.put(get); wrongly uses Get with put. Delete delete = new Delete(Bytes.toBytes("row1")); table.put(delete); uses Delete with put. Put put = new Put("row1"); put.add("cf", "qual", "value"); table.get(put); uses wrong constructors and methods.

3. Final Answer:

   Put put = new Put(Bytes.toBytes("row1")); put.addColumn(Bytes.toBytes("cf"), Bytes.toBytes("qual"), Bytes.toBytes("value")); table.put(put); -> Option C

4. Quick Check:

   Put syntax correct = Put put = new Put(Bytes.toBytes("row1")); put.addColumn(Bytes.toBytes("cf"), Bytes.toBytes("qual"), Bytes.toBytes("value")); table.put(put); [OK]

Hint: Put needs Bytes.toBytes for all keys and values [OK]

Common Mistakes:

• Using Get or Delete with put()
• Not converting strings to bytes
• Wrong method names like add() instead of addColumn()

3. What will be the output of the following HBase Java code snippet?

Put put = new Put(Bytes.toBytes("row1"));
put.addColumn(Bytes.toBytes("cf"), Bytes.toBytes("name"), Bytes.toBytes("Alice"));
table.put(put);

Get get = new Get(Bytes.toBytes("row1"));
Result result = table.get(get);
byte[] value = result.getValue(Bytes.toBytes("cf"), Bytes.toBytes("name"));
System.out.println(Bytes.toString(value));

medium

A. Compilation Error

B. null

C. cf:name

D. Alice

Solution

1. Step 1: Insert data with Put operation

   The code puts value "Alice" in column family "cf" and qualifier "name" for row "row1".

2. Step 2: Retrieve data with Get operation

   The Get fetches the row "row1" and extracts the value for "cf:name" which is "Alice".

3. Final Answer:

   Alice -> Option D

4. Quick Check:

   Put then Get returns inserted value [OK]

Hint: Put then Get returns inserted value exactly [OK]

Common Mistakes:

• Expecting null if not flushed
• Confusing column family and qualifier
• Forgetting to convert bytes to string

4. Identify the error in the following HBase delete operation code snippet:

Delete delete = new Delete("row1");
delete.addColumn(Bytes.toBytes("cf"), Bytes.toBytes("qual"));
table.delete(delete);

medium

A. Delete constructor argument should be bytes, not string

B. addColumn method is deprecated, should use addColumns

C. table.delete() method does not exist

D. No error, code is correct

Solution

1. Step 1: Check Delete constructor parameter type

   The Delete constructor requires a byte array for the row key, not a plain string.

2. Step 2: Verify method usage

   addColumn is valid for deleting a specific column. table.delete() is correct method.

3. Final Answer:

   Delete constructor argument should be bytes, not string -> Option A

4. Quick Check:

   Delete row key must be bytes [OK]

Hint: Always convert row keys to bytes in HBase operations [OK]

Common Mistakes:

• Passing string directly instead of bytes
• Confusing addColumn with addColumns
• Thinking table.delete() is invalid

5. You want to update the value of a column "status" in column family "info" for row "user123" in HBase. Which sequence of operations is correct to ensure the update is saved and can be read back immediately?

hard

A. Create a Delete for the old value, call table.delete(delete), then create a Put with new value and call table.put(put)

B. Create a Put with new value, call table.put(put), then call table.get(get) to read updated value

C. Call table.get(get) first, then create a Put with new value and call table.put(put)

D. Create a Put with new value, call table.get(get), then call table.put(put)

Solution

1. Step 1: Use Put to update the column value

   In HBase, Put operation overwrites existing values for the same column, so create a Put with the new "status" value for "user123".

2. Step 2: Save and verify update

   Call table.put(put) to save the update, then use table.get(get) to read back the updated value immediately.

3. Final Answer:

   Create a Put with new value, call table.put(put), then call table.get(get) to read updated value -> Option B

4. Quick Check:

   Put updates value, Get reads updated value [OK]

Hint: Put overwrites; Get reads latest value after put [OK]

Common Mistakes:

• Deleting before putting is unnecessary
• Getting before putting returns old value
• Calling get before put misses update