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From "ASF subversion and git services (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DERBY-6419) Make BTree scan honor OPENMODE_LOCK_NOWAIT for row locks.
Date Wed, 11 Dec 2013 13:40:07 GMT

    [ https://issues.apache.org/jira/browse/DERBY-6419?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13845384#comment-13845384
] 

ASF subversion and git services commented on DERBY-6419:
--------------------------------------------------------

Commit 1550135 from [~dagw] in branch 'code/trunk'
[ https://svn.apache.org/r1550135 ]

DERBY-6419 Make BTree scan honor OPENMODE_LOCK_NOWAIT for row locks

Patch derby-6419-1 introduces a mode to avoid waiting for row locks in
BTeee scans.  Using the debugger I can see that the current wait in
ConstraintCharactericsTest#testLocking, line 417 as of svn 1545394 is
no longer waiting with the patch, and stepping through the code in
IndexChanger I can see that the second next() which currently waits
returns immediately with an exception as desired.

Instead of overloading the current flag OPENMODE_LOCK_NOWAIT, I
introduced a new flag OPENMODE_LOCK_ROW_NOWAIT instead. The short
circuiting logic was added in B2IRowLocking3#LockRowOnPage: I had to
added an accessor to HeapController to get at the open_mode of the
base table's conglomerate; not sure if that's kosher or not. An
alternative could be to keep to flag in the B2IForwardScan object.

> Make BTree scan honor  OPENMODE_LOCK_NOWAIT for row locks.
> ----------------------------------------------------------
>
>                 Key: DERBY-6419
>                 URL: https://issues.apache.org/jira/browse/DERBY-6419
>             Project: Derby
>          Issue Type: Sub-task
>          Components: Store
>            Reporter: Dag H. Wanvik
>         Attachments: derby-6419-1.diff, derby-6419-1.status, derby-6419-followup.diff,
derby-6419-followup.status
>
>
> Optimization desirable to support deferred constraints.



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