Em 28/04/2014 12:01, Tom Lane escreveu:
Edson Richter <edsonrichter@xxxxxxxxxxx> writes:
When I issue a
select max(id) from MyTableName
Postgres 9.2.7 is scaling a AccessExclusiveLock and causing large delays.
Really?
regression=# create table MyTableName (
regression(# id integer not null primary key,
regression(# seqYear char(4),
regression(# seqCount integer);
NOTICE: CREATE TABLE / PRIMARY KEY will create implicit index "mytablename_pkey" for table "mytablename"
CREATE TABLE
regression=# begin;
BEGIN
regression=# select max(id) from MyTableName;
max
-----
(1 row)
regression=# select * from pg_locks;
locktype | database | relation | page | tuple | virtualxid | transactionid | classid | objid | objsubid | virtualtransaction | pid | mode | granted | fastpath
------------+----------+----------+------+-------+------------+---------------+---------+-------+----------+--------------------+-------+-----------------+---------+----------
relation | 16384 | 11069 | | | | | | | | 2/120853 | 12432 | AccessShareLock | t | t
relation | 16384 | 42142 | | | | | | | | 2/120853 | 12432 | AccessShareLock | t | t
relation | 16384 | 42139 | | | | | | | | 2/120853 | 12432 | AccessShareLock | t | t
virtualxid | | | | | 2/120853 | | | | | 2/120853 | 12432 | ExclusiveLock | t | t
(4 rows)
I see nothing higher than AccessShareLock on the table.
regards, tom lane
Really big sorry!!!
The programmer added a
LOCK TABLE MyTableName
just before issuing the select max(id) from MyTableName.
I do suspect this is the case, right?
Really sorry, I should have look into the code before asking!
Thanks for your (always) fast support.
Regards,
Edson
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