.tip

Apr 30, 2026 · one of the small things

Start every shell script with set -euo pipefail

By default a shell script carries on after a failed command, treats an unset variable as an empty string, and calls a pipeline successful as long as its last command succeeded. Three lines fix all of that.

#!/usr/bin/env bash
set -euo pipefail

You'll hit cases where you want a command to fail quietly. Write cmd || true there, deliberately, where a reader can see it.

shell

~/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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