Which SQL command creates ExclusiveLock? - Mailing list pgsql-sql

From Denis Khabas
Subject Which SQL command creates ExclusiveLock?
Date
Msg-id 5DEC3FFCDE2F7C4DA45433EE09A4F22C013457FF@colossus.dyadem.corp
Whole thread Raw
Responses Re: Which SQL command creates ExclusiveLock?  (Tom Lane <tgl@sss.pgh.pa.us>)
List pgsql-sql
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

 

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