Hi,
while playing a bit with pg_locks I came across this:
https://www.postgresql.org/docs/current/view-pg-locks.html
"Although tuples are a lockable type of object, information about row-level locks is stored on disk, not in memory, and
thereforerow-level locks normally do not appear in this view. If a process is waiting for a row-level lock, it will
usuallyappear in the view as waiting for the permanent transaction ID of the current holder of that row lock."
Given this? (I've just updated the same row in two transactions):
postgres=# select locktype,database::regdatabase,relation::regclass,pid,mode,granted,waitstart,page,tuple from pg_locks
wherepid != pg_backend_pid() order by pid;
locktype | database | relation | pid | mode | granted | waitstart | page | tuple
---------------+----------+----------+------+------------------+---------+-------------------------------+------+-------
relation | postgres | t | 9673 | RowExclusiveLock | t | | |
virtualxid | | | 9673 | ExclusiveLock | t | | |
transactionid | | | 9673 | ExclusiveLock | t | | |
virtualxid | | | 9691 | ExclusiveLock | t | | |
transactionid | | | 9691 | ShareLock | f | 2026-01-08 09:58:38.867534+01 | |
tuple | postgres | t | 9691 | ExclusiveLock | t | | 0 | 5
transactionid | | | 9691 | ExclusiveLock | t | | |
relation | postgres | t | 9691 | RowExclusiveLock | t | | |
(8 rows)
... I am wondering if that paragraph is still true or at least needs some adjustments to explain what "normally" and
"usually"means? There clearly is information about the tuple and the row level lock.
Regards
Daniel
