Eugene 🔒 trace report of examples/W14/bad/1.sql
Statement number 1 for 10ms
SQL
-- 1.sql
create table authors(
name text
)
Locks at start
No locks held at the start of this statement.
New locks taken
No new locks taken by this statement.
Eugene 🔒 trace report of examples/W14/bad/2.sql
Statement number 1 for 10ms
SQL
-- 2.sql
create unique index concurrently
authors_name_key on authors(name)
Locks at start
No locks held at the start of this statement.
New locks taken
No new locks taken by this statement.
Eugene 🔒 trace report of examples/W14/bad/3.sql
Statement number 1 for 10ms
SQL
-- 3.sql
set local lock_timeout = '2s'
Locks at start
No locks held at the start of this statement.
New locks taken
No new locks taken by this statement.
Statement number 2 for 10ms
SQL
alter table authors
add constraint authors_name_pkey
primary key using index authors_name_key
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 |
Hints
Validating table with a new constraint
ID: E1
A new constraint was added and it is already VALID. This blocks all table access until all rows are validated. A safer way is: Add the constraint as NOT VALID and validate it with ALTER TABLE ... VALIDATE CONSTRAINT later.
A new constraint authors_name_pkey of type PRIMARY KEY was added to the table public.authors as VALID. Constraints that are NOT VALID can be made VALID by ALTER TABLE public.authors VALIDATE CONSTRAINT authors_name_pkey which takes a lesser lock.
Validating table with a new NOT NULL column
ID: E2
A column was changed from NULL to NOT NULL. This blocks all table access until all rows are validated. A safer way is: Add a CHECK constraint as NOT VALID, validate it later, then make the column NOT NULL.
The column name in the table public.authors was changed to NOT NULL. If there is a CHECK (name IS NOT NULL) constraint on public.authors, this is safe. Splitting this kind of change into 3 steps can make it safe:
- Add a
CHECK (name IS NOT NULL) NOT VALID;constraint onpublic.authors. - Validate the constraint in a later transaction, with
ALTER TABLE public.authors VALIDATE CONSTRAINT .... - Make the column
NOT NULL