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https://issues.apache.org/jira/browse/CASSANDRA-2893?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13174911#comment-13174911
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Jonathan Ellis commented on CASSANDRA-2893:
-------------------------------------------
On the code side: should we just get rid of AbstractColumnContainer now since
it's basically just a wrapper around ISortedColumns?
Doesn't Guava Functions.identity do the same as ACC.identity?
{quote}
+ * In case we are adding a lot of columns, failing the final compare
+ * and swap could be expensive. To mitigate, we check we haven't been
+ * beaten by another thread after every column addition. If we have,
+ * we bail early, avoiding unnecessary work if possible.
{quote}
I wonder if this is premature optimization or even counterproductive for the
uncontended case. Did you do any testing around this?
More generally it may be worth looking at the before- and after- yourkit traces
for uncontended to see if there's any improvement we can make in
AtomicSortedColumns or if most of the overhead is from SnapTreeMap.
> Add row-level isolation
> -----------------------
>
> Key: CASSANDRA-2893
> URL: https://issues.apache.org/jira/browse/CASSANDRA-2893
> 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, 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 http://code.google.com/p/pcollections/ 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
> http://code.google.com/p/actord/source/browse/trunk/actord/src/main/scala/ff/collection
> (in scala) and http://clojure.org/data_structures#Data Structures-Maps.
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