How to Create an Index Concurrently in PostgreSQL (Zero Downtime)
Build a production database index on a table with millions of rows without locking out live INSERT, UPDATE, or DELETE operations.
CREATE INDEX CONCURRENTLY idx_users_email
ON users (email);Step-by-Step Query Breakdown
CREATE INDEX CONCURRENTLY idx_orders_customer_date
ON orders (customer_id, order_date DESC);Takes two table passes to build the index in the background without acquiring a write lock on the table.
CREATE UNIQUE INDEX CONCURRENTLY idx_unique_tenant_subdomain
ON tenants (subdomain);Enforces unique constraints in production without downtime.
SELECT indisvalid, indexrelid::regclass
FROM pg_index
WHERE NOT indisvalid;If a concurrent build fails (e.g. timeout or duplicate violation), Postgres leaves an invalid index that must be dropped and rebuilt.
DROP INDEX CONCURRENTLY IF EXISTS idx_users_email;Safely removes an invalid or obsolete index without write locks.
Critical SQL Pitfalls & Precautions
- •CREATE INDEX CONCURRENTLY cannot be run inside a transaction block (BEGIN ... COMMIT). Must be run as an individual auto-commit command.
- •It takes about 2-3x longer to build than a locked index because it performs two full table scans.
Create Index Concurrently (Zero Locks) - Frequently Asked Questions
Common questions about transactional safety, indexing, and engine compatibility.
Standard CREATE INDEX takes a SHARE lock that allows SELECT queries but blocks all INSERT, UPDATE, and DELETE queries until indexing finishes.
Related SQL Query Guides
Browse All SQL RecipesIdentify rows with duplicate column values using GROUP BY and HAVING count(*) > 1, and safely remove duplicates using ROW_NUMBER() CTEs.
Compare row-by-row logging (DELETE), fast table emptying with auto-increment reset (TRUNCATE), and complete table removal (DROP).
Atomically insert a new row or update an existing row if a unique constraint or primary key conflict is encountered.
Compute cumulative running totals over time or partitioned groups using SUM() OVER (ORDER BY ...).
Update values in one table based on matching columns or aggregations in a secondary table.
Reset the next auto-generated primary key ID back to 1 or synchronize it with the maximum existing ID in the table.