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From "Mike Matrigali (JIRA)" <j...@apache.org>
Subject [jira] Updated: (DERBY-2107) Move page latching out of the lock manager
Date Thu, 14 Dec 2006 21:47:22 GMT
     [ http://issues.apache.org/jira/browse/DERBY-2107?page=all ]

Mike Matrigali updated DERBY-2107:
----------------------------------


Dan is absolutely right about the unlatch() call.  Once unlatch call is made the page is free
to be thrown out of the cache and be replaced by a different page, from possibly a different
table, different page size ....
Once you call unlatch you have to reload the buffer manager, the problem is that you can't
do it in the interfaces you have
as the callers still have the old reference.  The btree code does this in it's code that manages
latch/lock outside of 
lockmanager.  For btree it was necessary as after you gave up latch while waiting on lock
the row could move off the 
original page.

For heap rows don't ever move off the page.  They can "disappear" in the purge case described
above, and in the 
offline compress case which is handled by a table level lock.



> Move page latching out of the lock manager
> ------------------------------------------
>
>                 Key: DERBY-2107
>                 URL: http://issues.apache.org/jira/browse/DERBY-2107
>             Project: Derby
>          Issue Type: Improvement
>          Components: Store, Services, Performance
>    Affects Versions: 10.3.0.0
>            Reporter: Knut Anders Hatlen
>         Assigned To: Knut Anders Hatlen
>            Priority: Minor
>         Attachments: derby-2107-1a.diff, derby-2107-1a.stat, derby-2107-1b.diff
>
>
> Latching of pages could be done more efficiently locally in store than in the lock manager.
See the discussion here: http://thread.gmane.org/gmane.comp.apache.db.derby.devel/33135

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