Optimizing Queries with Indexes (Secondary Indexes) in Cassandra

What are Indexes and Secondary Indexes

In a database, an index is a data structure used to accelerate data retrieval. A secondary index is an index associated with a table, which can be used for operations such as sorting and pagination on the table.

Why Use Indexes and Secondary Indexes

Using indexes and secondary indexes can significantly improve query performance, especially in large databases. They achieve this by reducing the cost of data retrieval.

How to Use Indexes and Secondary Indexes

1. Analyze the Query Plan

First, analyze your SQL query plan to determine which operations will have the greatest impact on performance.

2. Identify Available Indexes

Then, check whether indexes have been created on your table and ensure they are suitable for your queries. Typically, columns used frequently can be used as secondary indexes to improve query performance.

3. Create Secondary Indexes

Add or create new indexes on your table to improve query performance.

4. Optimize Table Structure

Depending on your SQL queries and data distribution, you may need to optimize the table structure to achieve better performance.

Examples

CREATE TABLE users (
    id INT PRIMARY KEY,
    name VARCHAR(255),
    email VARCHAR(255)
);

CREATE INDEX idx_name ON users (name);

1. Use a Secondary Index to Find Users

You can use the following SQL statement to find users whose names contain a specific character:

SELECT * FROM users WHERE name LIKE '%john%';

2. Use a Secondary Index to Find Users

You can also use the following SQL statement to find users whose email addresses contain a specific character:

SELECT * FROM users WHERE email LIKE '%@example.com';

Summary

Using indexes and secondary indexes is an important step in improving query performance. By analyzing your SQL query plan, identifying available indexes, and creating indexes suitable for your queries, you can significantly improve the performance of your application.