Repeated ALTER TABLE statements on the same table

Note — this works and blocks nothing, but a performance regression is likely.

What it catches

Each ALTER TABLE statement acquires its own ACCESS EXCLUSIVE lock — queueing behind traffic every single time. One ALTER TABLE with comma-separated actions acquires the lock once and does all the work under it.

Fires on

ALTER TABLE orders ADD COLUMN a text;
ALTER TABLE orders ADD COLUMN b text;

Do this instead

Combine the actions into one ALTER TABLE statement with comma-separated subcommands: one lock acquisition, one queue traversal, all the work done under it.

SET lock_timeout = '5s';
ALTER TABLE orders
  ADD COLUMN a text,
  ADD COLUMN b text;

Catch this before it ships

This rule runs in the hosted service on Startup and above — add --remote with a team token, or use the GitHub Action: npx bolvrk check migration.sql

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