.tip

Dec 4, 2025 · one of the small things

text, not varchar(255)

In Postgres, text and varchar(n) perform exactly the same. The length limit is just a check constraint with a worse error message, and changing it later takes a migration.

name text NOT NULL CHECK (length(name) <= 200)

If you need a limit, write it as a constraint you can drop or change without rewriting the column type.

postgresqlschema-design

~/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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