How to CREATE INDEX in PostgreSQL

How do I create an index in PostgreSQL to speed up queries?

CREATE INDEX builds an auxiliary data structure that accelerates SELECT queries by letting PostgreSQL locate rows without scanning the entire table.

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Description

What problem does CREATE INDEX solve?

Slow query performance often comes from full-table scans. CREATE INDEX adds a separate, ordered data map so PostgreSQL can jump straight to the rows you need, cutting I/O and latency dramatically.

When should I add an index in ecommerce apps?

Add indexes to columns frequently used in WHERE, JOIN, ORDER BY, or DISTINCT clauses. Typical picks are Orders.customer_id, OrderItems.order_id, and Products.name for keyword search.

Which index types does PostgreSQL offer?

B-tree (default) fits exact matches and range queries. Hash works for equality only. GIN/GiST handle JSONB or full-text search, while BRIN helps on large, naturally ordered tables like Orders(order_date).

How do I write the CREATE INDEX statement?

Use CREATE INDEX, optionally add CONCURRENTLY to avoid table locks, pick a descriptive name, and list columns in the most selective order.

Can I create conditional or partial indexes?

Yes. Add a WHERE clause to index only rows that matter, e.g., recent orders, reducing size while boosting performance where it counts.

How do I verify my index is used?

Run EXPLAIN (ANALYZE, BUFFERS) before and after indexing. Look for Index Scan or Index Only Scan nodes and lower total cost in the plan.

Best practices for CREATE INDEX

Name indexes consistently: table_column_idx. Avoid redundant indexes—PostgreSQL can use a multi-column index for the leading column alone. Reindex or drop unused indexes to save storage.

Why How to CREATE INDEX in PostgreSQL is important

How to CREATE INDEX in PostgreSQL Example Usage


-- Speed up recent orders lookup per customer
CREATE INDEX idx_orders_customer_recent
ON Orders (customer_id)
WHERE order_date >= CURRENT_DATE - INTERVAL '30 days';

How to CREATE INDEX in PostgreSQL Syntax


CREATE [UNIQUE] INDEX [CONCURRENTLY] [IF NOT EXISTS] index_name
    ON table_name [USING method] (column1 [ASC|DESC] [NULLS { FIRST | LAST }],
                                  column2, ...)
    [INCLUDE (non_key_column [, ...])]
    [WHERE predicate];

Example for ecommerce:
CREATE INDEX CONCURRENTLY IF NOT EXISTS idx_orders_customer_date
ON Orders USING btree (customer_id, order_date DESC);
-- Speeds up: SELECT * FROM Orders WHERE customer_id = 42 ORDER BY order_date DESC;

Common Mistakes

Creating too many overlapping indexes—each one slows down INSERT/UPDATE operations and wastes storage. Fix by auditing pg_stat_user_indexes and dropping rarely used indexes.
Forgetting CONCURRENTLY in production—plain CREATE INDEX locks writes, causing downtime. Always use CONCURRENTLY for large tables unless inside a maintenance window.