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Date: Wed, 15 Jul 2009 06:19:14 -0700 (PDT)
From: "Knut Anders Hatlen (JIRA)" <jira@apache.org>
To: derby-dev@db.apache.org
Subject: [jira] Commented: (DERBY-4302) Deadlock on system tables
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    [ https://issues.apache.org/jira/browse/DERBY-4302?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12731430#action_12731430 ] 

Knut Anders Hatlen commented on DERBY-4302:
-------------------------------------------

It looks like the deadlock is between a CREATE TABLE statement and a SELECT statement against the table that is about to be created. Issuing such statements concurrently is very likely to break. With slightly different timing, it could just as well have failed with a "table CORE_FILE does not exist" error instead of a deadlock.

> Deadlock on system tables
> -------------------------
>
>                 Key: DERBY-4302
>                 URL: https://issues.apache.org/jira/browse/DERBY-4302
>             Project: Derby
>          Issue Type: Bug
>          Components: SQL
>            Reporter: Egidijus
>
> Using 3d part libraries which uses embedded Derby DB, I got following stack trace which shows that deadlock appears between *system* tables (unfortunately there are no code to reproduce). Connecting without auto commit and DB is used by two users: 
> Lock : TABLE, SYSCOLUMNS, Tablelock
>   Waiting XID : {9404, IS} , APP, SELECT cdo_version, cdo_created,
> cdo_revised, cdo_resource, cdo_container, cdo_feature, name, id FROM
> core_File WHERE cdo_id= ? AND (cdo_revised = 0 )
>   Granted XID : {7351, IX}
> Lock : ROW, SYSTABLES, (2,14)
>   Waiting XID : {7351, X} , APP, CREATE TABLE core_File (cdo_id BIGINT
> NOT NULL, cdo_version INTEGER NOT NULL, cdo_class BIGINT NOT NULL,
> cdo_created BIGINT NOT NULL, cdo_revised BIGINT NOT NULL, cdo_resource
> BIGINT NOT NULL, cdo_container BIGINT NOT NULL, cdo_feature INTEGER
> NOT NULL, name VARCHAR(32672), id VARCHAR(32672))
>   Granted XID : {9404, S}
> . The selected victim is XID : 9404. 

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