#schema-design

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UUIDv7 and the end of the random primary key

PostgreSQL 18 ships uuidv7() in core. It looks like a small convenience function, and it ends a decade-long argument about UUID primary keys. The numbers from a 200 million row table show why. The migration path is included, along with the one gotcha around the timestamp you can extract.

postgresqldatabaseperformance+1 more

Apr 28, 202611 min14 min

~/tips/today — 2026-10-19

~cat tips/today

Never build an index on a live table without CONCURRENTLY

postgresqlmigrations

A plain CREATE INDEX takes a lock that blocks every write to the table for the whole build. On a big table that means minutes of outage that look like a hung app.

CREATE INDEX CONCURRENTLY orders_customer_idx ON orders (customer_id);

It's slower and can't run inside a transaction, so you'll have to tell your migration tool. If it fails halfway, it leaves an invalid index behind, so check pg_index.indisvalid and drop it before you retry.

↵ open y yesterday l ls /tips

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