Index creation in Ruby on Rails - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is an index in a database?

An index is like a shortcut that helps the database find data faster, similar to an index in a book that points to pages quickly.

beginner

How do you create an index on a column in Rails migrations?

You use add_index :table_name, :column_name inside a migration file to create an index on that column.

intermediate

Why should you use indexes carefully?

Indexes speed up reading data but slow down writing data because the index needs updating. So, use them only on columns you search often.

intermediate

What does a unique index do?

A unique index makes sure that all values in the indexed column are different, preventing duplicate entries.

beginner

How do you remove an index in Rails?

You use remove_index :table_name, :column_name in a migration to delete an index.

Which Rails migration command creates an index on the 'email' column of the 'users' table?

A add_column :users, :email_index

B create_index :users, :email

C add_index :users, :email

D index_add :users, :email

The correct syntax to add an index is add_index :table_name, :column_name.

What is the main benefit of adding an index to a database column?

A Faster data retrieval

B More storage space

C Slower queries

D Automatic backups

Indexes help the database find data faster, improving query speed.

What is a potential downside of having too many indexes?

A Slower data insertion and updates

B Faster data insertion

C No effect on performance

D Database crashes

Indexes need updating when data changes, which can slow down insert and update operations.

How do you enforce uniqueness of values in a column using an index in Rails?

A add_unique_index :table, :column

B add_index :table, :column, unique: true

C add_index :table, :column, unique: false

D create_unique :table, :column

You add unique: true option to add_index to enforce uniqueness.

Which command removes an index on the 'username' column in the 'accounts' table?

A drop_index :accounts, :username

B remove_column :accounts, :username

C delete_index :accounts, :username

D remove_index :accounts, :username

The correct command to remove an index is remove_index :table_name, :column_name.

Explain what a database index is and why it is useful.

Think about how you find a topic quickly in a book.

Describe how to create and remove an index in Rails migrations.

Use Rails migration commands for managing indexes.