E5 Type change requiring table rewrite
Description
Triggered when: A column was changed to a data type that isn't binary compatible.
Effect: This causes a full table rewrite while holding a lock that prevents all other use of the table.
Workaround: Add a new column, update it in batches, and drop the old column.
Detected by: eugene lint and eugene trace
Problematic migration
-- 1.sql
create table prices (
id integer generated always as identity
primary key,
price int not null
);
-- 2.sql
set local lock_timeout = '2s';
alter table prices
alter price set data type bigint;
Safer migration
-- 1.sql
create table prices (
id integer generated always as identity
primary key,
price int not null
);
-- 2.sql
set local lock_timeout = '2s';
alter table prices
add column new_price bigint;
-- 3.sql
update prices set new_price = price :: bigint;
set local lock_timeout = '2s';
alter table prices
add constraint check_new_price_not_null
check (new_price is not null) not valid;
-- 4.sql
set local lock_timeout = '2s';
alter table prices
validate constraint check_new_price_not_null,
drop column price;
-- eugene: ignore E4
-- this has to run in the same transaction as dropping the old price column
alter table prices
rename column new_price to price;