How to Add an Index in PostgreSQL

Adding an index in PostgreSQL can dramatically improve the performance of your queries, especially on large tables. This tutorial will walk you through why indexes matter, how to create them, and some best practices.

Why Add an Index?

An index is like a roadmap for your database — it helps PostgreSQL quickly locate rows that match a query, reducing the time it takes to fetch results. Without indexes, PostgreSQL has to scan the entire table, which can be very slow.

Basic Syntax

CREATE INDEX index_name ON table_name (column_name);

Example:

CREATE INDEX idx_users_email ON users (email);

When to Use Indexes

• On columns frequently used in WHERE clauses
• On columns used in JOIN conditions
• On columns used in ORDER BY clauses
• On columns with many unique values

Types of Indexes

PostgreSQL supports several index types:

• BTREE (default): good for equality and range queries
• HASH: good for equality comparisons
• GIN: good for array, JSONB, and full-text search
• GiST: good for geometric data

Creating a Specific Index Type

CREATE INDEX index_name ON table_name USING GIN (column_name);

Example:

CREATE INDEX idx_posts_tags ON posts USING GIN (tags);

Best Practices

• Only index columns you query often — too many indexes can slow down writes.
• Use meaningful index names (e.g., idx_table_column).
• Regularly monitor and analyze index usage with pg_stat_user_indexes.
• Consider partial or conditional indexes for selective queries.

Conclusion

Adding indexes is one of the easiest and most powerful ways to optimize your PostgreSQL database. Use them wisely to strike the right balance between read performance and write overhead.

For more details, check the official PostgreSQL Indexes documentation.