Speed Up Exact Match Queries with a Hash Index

Create a Hash Index for Equality Search

Write a PostgreSQL query to create a hash index on the "username" column in the Users table.

Solution:

-- Create a hash index on the "username" column.
CREATE INDEX idx_users_username_hash ON Users USING hash (username);

Explanation:

• Purpose of the Query:
• To optimize queries that perform equality searches on the "username" column.
• Illustrates the use of a hash index, which is tailored for equality comparisons.
• Key Components:
• USING hash specifies the hash index type.
• (username) indicates the column on which the index is built.
• Real-World Application:
• Ideal for lookups where exact matches are required, such as login validations

Notes:

• Hash indexes only support equality operators (e.g., =).
• They are not useful for range queries.
• Use hash indexes when your query patterns primarily involve exact matches.

For more Practice: Solve these Related Problems:

• Write a PostgreSQL query to create a hash index on the "username" column in the "Users" table.
• Write a PostgreSQL query to create a hash index on the "serial_number" column in the "Devices" table.
• Write a PostgreSQL query to create a hash index on the "isbn" column in the "Books" table for fast exact-match searches.
• Write a PostgreSQL query to create a hash index on the "passport_number" column in the "Citizens" table.

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• Hands-on PostgreSQL Indexing Techniques and Exercises Home. ↩
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