W12 Multiple ALTER TABLE statements where one will do
Description
Triggered when: Multiple ALTER TABLE statements targets the same table.
Effect: If the statements require table scans, there will be more scans than necessary.
Workaround: Combine the statements into one, separating the action with commas.
Detected by: eugene lint
Problematic migration
-- 1.sql
create table authors(
id integer generated always as identity
primary key,
name text,
email text
);
-- 2.sql
set lock_timeout = '2s';
alter table authors
alter column name set not null;
-- eugene: ignore E2, E4
alter table authors
alter column email set not null;
Safer migration
-- 1.sql
create table authors(
id integer generated always as identity
primary key,
name text,
email text
);
-- 2.sql
set lock_timeout = '2s';
-- eugene: ignore E2
alter table authors
alter column name set not null,
alter column email set not null;