Re: Guarantee order of batched pg_advisory_xact_lock

I just checked for hash collisions with the following query today:

SELECT COUNT(*), hashtextextended(key, 0) FROM
(
  SELECT key FROM table1
  UNION
  SELECT key FROM table2
  UNION
  ...
) keys (key)
GROUP BY hashtextextended(key, 0)
HAVING COUNT(*) > 1

Where table1, table2, ... are all the tables we are acquire keys from to
use for the mentioned query.

Sadly, no results were returned. Thus, I can rule out hash collisions.

Any other thoughts? Here is an error log from the JDBC driver:

org.postgresql.util.PSQLException: ERROR: deadlock detected Detail:
Process 60780 waits for ExclusiveLock on advisory lock
[24605,3030106527,494580150,1]; blocked by process 65280.
 Process 65280 waits for ExclusiveLock on advisory lock
[24605,1321834016,1311356115,1]; blocked by process 60780.

On 2/11/26 23:49, Tom Lane wrote:
> Nico Heller<nico(dot)heller(at)posteo(dot)de> writes:
>> So it would probably be better to ORDER BY the hashtextended result
>> instead of :keysToLock, right?
> Yeah, that seems like it'd work, if you have no other dependencies
> on the locking order.
>
> regards, tom lane