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From "Jonathan Ellis (Updated) (JIRA)" <>
Subject [jira] [Updated] (CASSANDRA-2893) Add row-level isolation
Date Fri, 27 Jan 2012 14:38:10 GMT


Jonathan Ellis updated CASSANDRA-2893:

    Attachment: 2893-pauses.txt

I can also reproduce the apparently atomic insert behavior in 1.0.  I'm not sure what quirk
of Java optimization is causing it, to be honest.  But I'm not worried about it because when
I forced pauses between the columns being added ("pauses" patch attached) then I did see the
counts change.  (Specifically, I initialized the row first with "stress -t 1 -n 1 -c 1 -K
1", then sent 10000 columns with "stress -t 1 -n 1 -c 10000 -K 1".)  

So whatever is making the updates highly likely to be isolated does not *guarantee* it, so
I'm comfortable that our mental model of the 1.0 Memtable is valid.

> Add row-level isolation
> -----------------------
>                 Key: CASSANDRA-2893
>                 URL:
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: Jonathan Ellis
>            Assignee: Sylvain Lebresne
>            Priority: Minor
>             Fix For: 1.1
>         Attachments: 0001-Move-deletion-infos-into-ISortedColumns-v2.patch, 0001-Move-deletion-infos-into-ISortedColumns.patch,
0002-Make-memtable-use-CF.addAll-v2.patch, 0002-Make-memtable-use-CF.addAll.patch, 0003-Add-AtomicSortedColumn-and-snapTree-v2.patch,
0003-Add-AtomicSortedColumn-and-snapTree.patch, 2893-pauses.txt, latency-plain.svg, latency.svg,, snaptree-0.1-SNAPSHOT.jar
> This could be done using an the atomic ConcurrentMap operations from the Memtable and
something like to replace the ConcurrentSkipListMap
in ThreadSafeSortedColumns.  The trick is that pcollections does not provide a SortedMap,
so we probably need to write our own.
> Googling [persistent sortedmap] I found
(in scala) and Structures-Maps.

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