[SQL] Which SQL command creates ExclusiveLock?

[Denis Khabas]

Hi everyone!

 

I have a web application that uses Postgresql on backend. The application performs selects, updates, inserts, and deletes by using Hibernate. Tables

contain indexed fields. When I run the following query, SELECT * FROM pg_locks, it shows that some transactions place

ExclusiveLock:

 

 relation | database | transaction |  pid      |      mode       | granted
----------+----------+-------------+-------+-----------------+---------
    16757 |    16976 |                  | 22770  | AccessShareLock | t
              |             |    17965163 | 22770  | ExclusiveLock   | t

 

According to postgres documentation, all update operations place ROW EXCLUSIVE MODE locks, and

EXCLUSIVE MODE is not automatically acquired by any postgres SQL command. So, which command places

ExclusiveLock??? I suspect that indexes can account for this behaviour, but couldn't find anything in the docs.

I am also wondering why there is nothing shown in "relation" column. I think it is supposed to display a table or index id or any other

object that is being locked.

 

Thanks for help!

 

Dennis