CRUD operations in HBase in Hadoop

Introduction

CRUD operations let you create, read, update, and delete data in HBase. This helps manage big data easily.

When you want to add new records to a large database.

When you need to find specific data quickly.

When you want to change existing information in your database.

When you want to remove outdated or wrong data.

When working with big data that needs fast access and updates.

Syntax

Hadoop

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

Get get = new Get(Bytes.toBytes("row1"));
Result result = table.get(get);

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

Use Put to add or update data.

Use Get to read data.

Use Delete to remove data.

Examples

Adds a new row with a column 'name' set to 'Alice'.

Hadoop

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

Reads the value of 'name' from row 'row1' and prints it.

Hadoop

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));

Updates the 'name' column in 'row1' to 'Bob'.

Hadoop

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

Deletes the entire row 'row1'.

Hadoop

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

Sample Program

This program connects to HBase, adds a row, reads it, updates it, reads again, deletes it, and checks deletion.

Hadoop

import org.apache.hadoop.hbase.HBaseConfiguration;
import org.apache.hadoop.hbase.TableName;
import org.apache.hadoop.hbase.client.*;
import org.apache.hadoop.hbase.util.Bytes;

public class HBaseCRUDExample {
    public static void main(String[] args) throws Exception {
        org.apache.hadoop.conf.Configuration config = HBaseConfiguration.create();
        try (Connection connection = ConnectionFactory.createConnection(config)) {
            TableName tableName = TableName.valueOf("my_table");
            try (Table table = connection.getTable(tableName)) {
                // Create (Put)
                Put put = new Put(Bytes.toBytes("row1"));
                put.addColumn(Bytes.toBytes("cf"), Bytes.toBytes("name"), Bytes.toBytes("Alice"));
                table.put(put);

                // Read (Get)
                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("Read value: " + Bytes.toString(value));

                // Update (Put)
                Put putUpdate = new Put(Bytes.toBytes("row1"));
                putUpdate.addColumn(Bytes.toBytes("cf"), Bytes.toBytes("name"), Bytes.toBytes("Bob"));
                table.put(putUpdate);

                // Read updated value
                Result updatedResult = table.get(get);
                byte[] updatedValue = updatedResult.getValue(Bytes.toBytes("cf"), Bytes.toBytes("name"));
                System.out.println("Updated value: " + Bytes.toString(updatedValue));

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

                // Try to read deleted row
                Result deletedResult = table.get(get);
                if (deletedResult.isEmpty()) {
                    System.out.println("Row deleted successfully.");
                } else {
                    System.out.println("Row still exists.");
                }
            }
        }
    }
}

Important Notes

Always close HBase connections and tables to avoid resource leaks.

Put operation can add new data or update existing data.

Delete removes entire rows or specific columns if specified.

Summary

CRUD means Create, Read, Update, Delete data in HBase.

Use Put for create and update, Get for read, Delete for removal.

These operations help manage big data efficiently.

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