Thread: Postgresql Database Lock Problem
Problem: Database Lock ---------------------------------- Dear all I am working as a database administrator in a company. Our Database system is Postgresql-8.3.5 and Application server is Jboss used for our Adempiere ERP system. This is a web based ERP system. All servers are running on RHEL. Now our system is going to on-line and users are entering old data. So transactions are occurring very frequently. Now I am facing the problem is the application server just hangs at busy hour and it does not accept any new connection. When I restart the server (Adempiere, Jboss) it works fine for a few hours and problem occurs again. When this problem occurs the database server shows the following log LOG: process 19181 still waiting for ShareLock on transaction 18025221 after 1002.251 ms STATEMENT: SELECT CurrentNext, CurrentNextSys, IncrementNo, Prefix, Suffix, DecimalPattern, AD_Sequence_ID FROM AD_Sequence WHERE Name = $1 AND AD_Client_ID = $2 AND IsActive='Y' AND IsTableID='N' AND IsAutoSequence='Y' ORDER BY AD_Client_ID DESC FOR UPDATE OF AD_Sequence LOG: process 19181 acquired ShareLock on transaction 18025221 after 1298870.572 ms STATEMENT: SELECT CurrentNext, CurrentNextSys, IncrementNo, Prefix, Suffix, DecimalPattern, AD_Sequence_ID FROM AD_Sequence WHERE Name = $1 AND AD_Client_ID = $2 AND IsActive='Y' AND IsTableID='N' AND IsAutoSequence='Y' ORDER BY AD_Client_ID DESC FOR UPDATE OF AD_Sequence and the lock table informations are as following: adempiere=# select * from pg_locks where granted = 'y' and mode = 'ExclusiveLock'; locktype | database | relation | page | tuple | virtualxid | transactionid | classid | objid | objsubid | virtualtransaction | pid | mode | granted ---------------+----------+----------+------+-------+------------+---------------+---------+-------+----------+--------------------+-------+---------------+--------- transactionid | | | | | | 18386552 | | | | 39/1733 | 19196 | ExclusiveLock | t virtualxid | | | | | 24/1586 | | | | | 24/1586 | 19181 | ExclusiveLock | t transactionid | | | | | | 18386856 | | | | 24/1586 | 19181 | ExclusiveLock | t virtualxid | | | | | 39/1733 | | | | | 39/1733 | 19196 | ExclusiveLock | t transactionid | | | | | | 18386574 | | | | 39/1733 | 19196 | ExclusiveLock | t transactionid | | | | | | 18386563 | | | | 39/1733 | 19196 | ExclusiveLock | t transactionid | | | | | | 18386869 | | | | 24/1586 | 19181 | ExclusiveLock | t virtualxid | | | | | 50/20 | | | | | 50/20 | 19217 | ExclusiveLock | t transactionid | | | | | | 18386846 | | | | 24/1586 | 19181 | ExclusiveLock | t tuple | 250427 | 251989 | 209 | 7 | | | | | | 24/1586 | 19181 | ExclusiveLock| t (10 rows) adempiere=# select * from pg_locks where granted = 'f'; locktype | database | relation | page | tuple | virtualxid | transactionid | classid | objid | objsubid | virtualtransaction | pid | mode | granted ---------------+----------+----------+------+-------+------------+---------------+---------+-------+----------+--------------------+-------+-----------+--------- transactionid | | | | | | 18386574 | | | | 24/1586 | 19181 | ShareLock | f (1 row) *** Here you can see that process 19196 have ExclusiveLock on transaction 18386574 and process 19181 is waiting for ShareLock to the same transaction. When I monitor the Application server sessions from Jboss console normally I can see one of three stats R-Ready, K-Keep Alive and S-Service. When the application server hangs all sessions goes to Service mode. Please give me your appropriate and valuable solution in this regard. I am eagerly looking forward for your quick reply. Thanks in advance: --------------------------- Shohorab Hossain Send instant messages to your online friends http://uk.messenger.yahoo.com
Next time this is happening join the pg_lock table to the pg_stat_activity table to see which query is holding the lock for a bazillion milliseconds, while it's happening. That query / statement may give you some clue what's wrong.
The statement that creates lock and waiting is in following. This is from pg_stats and pg_stat_activity view.
Here AD_Sequence is a table that maintains sequence number for all database objects. It automatically generates primary
keyvalue for all table insert. I think it also generates transaction related ID. For that reason it needs to update
nextsequence value for transaction ID.
Statment:
======================
SELECT CurrentNext, CurrentNextSys, IncrementNo, Prefix, Suffix, DecimalPattern, AD_Sequence_ID FROM AD_Sequence WHERE
Name= $1 AND AD_Client_ID = $2 AND IsActive='Y' AND IsTableID='N' AND IsAutoSequence='Y' ORDER BY AD_Client_ID DESC FOR
UPDATEOF AD_Sequence
AD_Sequence Table Definition
=====================
adempiere=# \d ad_sequence
Table "adempiere.ad_sequence"
Column | Type | Modifiers
----------------+-----------------------------+------------------------------
ad_sequence_id | numeric(10,0) | not null
ad_client_id | numeric(10,0) | not null
ad_org_id | numeric(10,0) | not null
isactive | character(1) | default 'Y'::bpchar
created | timestamp without time zone | not null default now()
createdby | numeric(10,0) | not null
updated | timestamp without time zone | not null default now()
updatedby | numeric(10,0) | not null
name | character varying(60) | not null
description | character varying(255) |
vformat | character varying(40) |
isautosequence | character(1) | not null default 'Y'::bpchar
incrementno | numeric(10,0) | not null
startno | numeric(10,0) | not null
currentnext | numeric(10,0) | not null
currentnextsys | numeric(10,0) | not null
isaudited | character(1) | default 'N'::bpchar
istableid | character(1) | default 'N'::bpchar
prefix | character varying(255) |
suffix | character varying(255) |
startnewyear | character(1) | default 'N'::bpchar
datecolumn | character varying(60) |
decimalpattern | character varying(40) |
Indexes:
"ad_sequence_pkey" PRIMARY KEY, btree (ad_sequence_id)
"ad_sequence_name" UNIQUE, btree (ad_client_id, name)
Check constraints:
"ad_sequence_isactive_check" CHECK (isactive = ANY (ARRAY['Y'::bpchar, 'N'::bpchar]))
"ad_sequence_isaudited_check" CHECK (isaudited = ANY (ARRAY['Y'::bpchar, 'N'::bpchar]))
"ad_sequence_isautosequence_check" CHECK (isautosequence = ANY (ARRAY['Y'::bpchar, 'N'::bpchar]))
"ad_sequence_istableid_check" CHECK (istableid = ANY (ARRAY['Y'::bpchar, 'N'::bpchar]))
"ad_sequence_startnewyear_check" CHECK (startnewyear = ANY (ARRAY['Y'::bpchar, 'N'::bpchar]))
Foreign-key constraints:
"sequenceclient" FOREIGN KEY (ad_client_id) REFERENCES ad_client(ad_client_id) DEFERRABLE INITIALLY DEFERRED
"sequenceorg" FOREIGN KEY (ad_org_id) REFERENCES ad_org(ad_org_id) DEFERRABLE INITIALLY DEFERRED
With Thanks & Regards:
---------------------
Shohorab Hossain
----- Original Message ----
From: Scott Marlowe <scott.marlowe@gmail.com>
To: shohorab hossain <shohorab23@yahoo.com>
Cc: pgsql-admin@postgresql.org; pgsql-docs@postgresql.org; pgsql-general@postgresql.org
Sent: Wednesday, November 18, 2009 2:55:25
Subject: Re: [GENERAL] Postgresql Database Lock Problem
Next time this is happening join the pg_lock table to the
pg_stat_activity table to see which query is holding the lock for a
bazillion milliseconds, while it's happening. That query / statement
may give you some clue what's wrong.
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