E10 trace safer - Eugene Documentation

✅ Eugene trace report

Script name: examples/E10/good/1.sql

✅ Statement number 1 for 10ms

-- 1.sql
create table prices (
    id integer generated always as identity
        primary key,
    price int not null
)

Locks at start

No locks held at the start of this statement.

✅ Statement number 2 for 10ms

create table authors (
    id integer generated always as identity
        primary key,
    name text not null
)

Locks at start

No locks held at the start of this statement.

✅ Eugene trace report

Script name: examples/E10/good/2.sql

✅ Statement number 1 for 10ms

-- 2.sql
set local lock_timeout = '2s'

Locks at start

No locks held at the start of this statement.

✅ Statement number 2 for 10ms

alter table authors
    add column meta jsonb

Locks at start

No locks held at the start of this statement.

New locks taken

Schema	Object	Mode	Relkind	OID	Safe	Duration held (ms)
`public`	`authors`	`AccessExclusiveLock`	Table	1	❌	10

❌ Eugene trace report

Script name: examples/E10/good/3.sql

✅ Statement number 1 for 10ms

-- 3.sql
set local lock_timeout = '2s'

Locks at start

No locks held at the start of this statement.

❌ Statement number 2 for 10ms

-- eugene: ignore E5, E4
-- causes table rewrite, but this example isnt't about that
alter table prices
    alter price set data type bigint

Locks at start

No locks held at the start of this statement.

New locks taken

Schema	Object	Mode	Relkind	OID	Safe	Duration held (ms)
`public`	`prices`	`AccessExclusiveLock`	Table	1	❌	10
`public`	`prices`	`ShareLock`	Table	1	❌	10
`public`	`prices_pkey`	`AccessExclusiveLock`	Index	1	❌	10

Triggered rules

`E6`: Creating a new index on an existing table

A new index was created on the table public.prices. The index was created non-concurrently, which blocks all writes to the table. Use CREATE INDEX CONCURRENTLY to avoid blocking writes.

`E10`: Rewrote table or index while holding dangerous lock

The Table public.prices was rewritten while holding AccessExclusiveLock on the Table public.prices. This blocks SELECT, FOR UPDATE, FOR NO KEY UPDATE, FOR SHARE, FOR KEY SHARE, UPDATE, DELETE, INSERT, MERGE while the rewrite is in progress.