On 27.03.2013 15:07, roberto.menoncin@netspa.it wrote:
> 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