.tip

Apr 7, 2026 · one of the small things

A .dockerignore is the first file in a new Dockerfile's folder

Without one, COPY . . sends node_modules, .git and every local artefact to the build. That's slow, and now and then it ships a secret.

node_modules
.git
.next
*.log
.env*

The syntax is the same as .gitignore. Every build prints the context size at the start, and if it's more than a few megabytes, this file is missing something.

docker

~/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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