How to CREATE INDEX in PostgreSQL

How do I use CREATE INDEX to speed up queries?

CREATE INDEX builds a secondary data structure that accelerates WHERE, JOIN, ORDER BY, and GROUP BY look-ups without changing table data.

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Description

What problem does CREATE INDEX solve?

CREATE INDEX adds a fast-lookup structure beside the table, letting PostgreSQL avoid full scans when filtering Orders by customer_id or sorting Products by price.

How do I write basic CREATE INDEX syntax?

Use CREATE INDEX index_name ON table_name(column1 [,column2]);.The command names the index, selects the table, then lists one or more indexed columns.

Example: speed up customer email search

CREATE INDEX idx_customers_email ON Customers(email); lets PostgreSQL locate a customer’s row with O(log n) seeks instead of scanning every record.

Which index types are available?

PostgreSQL offers B-tree (default), Hash, GIN, GiST, BRIN, and SP-GiST.Choose B-tree for equality or range on scalar values, GIN for JSONB or array membership, and BRIN for huge, naturally ordered tables like Orders by order_date.

When should I include multiple columns?

Create a multicolumn index when queries filter by the same leading columns in the same order.Example: Orders filtered by (customer_id, order_date).

Example: composite B-tree

CREATE INDEX idx_orders_customer_date ON Orders(customer_id, order_date DESC); accelerates dashboards that show the latest orders per customer.

How do I create unique constraints with indexes?

Use UNIQUE to guarantee no duplicates. CREATE UNIQUE INDEX idx_products_name ON Products(name); ensures each product name is unique while speeding searches.

Can I index expressions?

Yes—wrap the expression in parentheses.CREATE INDEX idx_lower_email ON Customers(LOWER(email)); supports case-insensitive lookups without function calls in WHERE.

What are best practices?

Index selective columns, monitor with pg_stat_user_indexes, keep total indexes per table modest, and always test on staging. Drop unused indexes to save RAM and write overhead.

How do I remove or rename an index?

Drop with DROP INDEX IF EXISTS idx_name;. Rename with ALTER INDEX idx_old RENAME TO idx_new;.Both are quick metadata changes unless CONCURRENTLY was used.

Does CREATE INDEX block writes?

Plain CREATE INDEX holds exclusive locks that block writes. Use CREATE INDEX CONCURRENTLY to build in the background, at the cost of longer build time and extra disk.

How do I check if an index is used?

Run EXPLAIN ANALYZE; look for Index Scan or Bitmap Index Scan nodes. Also inspect pg_stat_user_indexes.idx_scan counters after normal workload.

Why How to CREATE INDEX in PostgreSQL is important

How to CREATE INDEX in PostgreSQL Example Usage


-- Speed dashboard filtering of high-value orders in the past year
CREATE INDEX idx_orders_amount_date ON Orders(total_amount DESC, order_date DESC);

-- Case-insensitive customer email searches
CREATE INDEX idx_lower_email ON Customers(LOWER(email));

How to CREATE INDEX in PostgreSQL Syntax


CREATE [UNIQUE] [CLUSTER] INDEX [CONCURRENTLY] index_name
    ON table_name [USING { btree | hash | gist | gin | brin | spgist }]
    ( column_name [ASC|DESC] [NULLS { FIRST | LAST }] [, ...] )
    [INCLUDE (column_name [, ...])]
    [WITH (storage_parameter = value [, ...])]
    [TABLESPACE tablespace_name];

-- Ecommerce examples
CREATE INDEX idx_customers_email       ON Customers(email);
CREATE UNIQUE INDEX idx_products_name  ON Products(name);
CREATE INDEX idx_orders_customer_date  ON Orders(customer_id, order_date DESC);
CREATE INDEX idx_orderitems_comp       ON OrderItems(order_id, product_id);
CREATE INDEX CONCURRENTLY idx_products_price ON Products(price);

Common Mistakes

Indexing every column. This bloats storage and slows INSERT/UPDATE. Fix by indexing only columns frequently used in WHERE, JOIN, ORDER BY, or UNIQUE constraints.
Ignoring index maintenance cost. An unused index consumes RAM and CPU during writes. Regularly review pg_stat_user_indexes and DROP indexes with low idx_scan counts.