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From "Jonathan Ellis (JIRA)" <j...@apache.org>
Subject [jira] Commented: (CASSANDRA-414) remove sstableLock
Date Sun, 06 Sep 2009 04:43:57 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-414?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12751824#action_12751824
] 

Jonathan Ellis commented on CASSANDRA-414:
------------------------------------------

I checked the source for NBHM and couldn't find any evidence that my literal reading of the
iterator contract ("Iterators and Enumerations return elements reflecting the state of the
hash table at some point at or since the creation of the iterator/enumeration") was correct.
 So I asked the author for clarification here: https://sourceforge.net/forum/message.php?msg_id=7611241.

He replied, and sure enough, Jun's suspicions were correct and even if the compaction thread
is careful to add the new SSTR before removing the old ones from sstables_, iterator threads
may see the absence of the latter but not the presence of the former.

So I think that this approach is not going to work.  But I think we can still cut the lock
penalty dramatically from what it is now.  I should have some code for that approach Monday.

> remove sstableLock
> ------------------
>
>                 Key: CASSANDRA-414
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-414
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>            Reporter: Jonathan Ellis
>            Assignee: Jonathan Ellis
>             Fix For: 0.5
>
>         Attachments: 0001-CASSANDRA-414-combine-addToList-and-storeLocation-ren.txt,
0001-CASSANDRA-414-combine-addToList-and-storeLocation-ren.txt, 0002-remove-sstableLock.-re-order-a-few-ops-so-that-we-can.txt,
0002-remove-sstableLock.-re-order-a-few-ops-so-that-we-can.txt
>
>


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