BUG #8000: ExclusiveLock on a simple SELECT ?

[r***@netspa.it]

The following bug has been logged on the website:

Bug reference: 8000
Logged by: Roberto
Email address: ***@netspa.it
PostgreSQL version: 9.2.3
Operating system: CentOS 5.6 (Final)
Description:

Hy,

after upgrading to version 9.2.3 we having a performance degradation.
We are investigating the matter on several fronts.
We've seen that Postgres (9.2.3) creates ExclusiveLock even with simple
SELECT * From myschema.mytable.

Is it normal ?

Thank you

[Heikki Linnakangas]

Post by r***@netspa.it
after upgrading to version 9.2.3 we having a performance degradation.
We are investigating the matter on several fronts.
We've seen that Postgres (9.2.3) creates ExclusiveLock even with simple
SELECT * From myschema.mytable.

You mean like this:

postgres=# create table mytable(i int4);
CREATE TABLE
postgres=# begin;
BEGIN
postgres=# select * from mytable;
i
---
(0 rows)

postgres=# select * from pg_locks;
locktype | database | relation | page | tuple | virtualxid |
transactionid |
classid | objid | objsubid | virtualtransaction | pid | mode
| gran
ted | fastpath
------------+----------+----------+------+-------+------------+---------------+-
--------+-------+----------+--------------------+-------+-----------------+-----
----+----------
relation | 12010 | 11069 | | | |
|
| | | 1/3 | 19811 |
AccessShareLock | t
| t
relation | 12010 | 16482 | | | |
|
| | | 1/3 | 19811 |
AccessShareLock | t
| t
virtualxid | | | | | 1/3 |
|
| | | 1/3 | 19811 | ExclusiveLock
| t
| t
(3 rows)

That last ExclusiveLock is on the transactions virtual transactaction
ID. Not on the table. There is no change from previous versions here.

- Heikki