.tip

Apr 18, 2026 · one of the small things

Turn on rerere before a long rebase

Rebasing a twenty commit branch over main means resolving the same conflict several times. rerere records how you resolved it the first time and replays that.

git config --global rerere.enabled true

It's off by default, and nobody remembers why. Turn it on once and you can forget it exists.

git

~/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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