[
https://issues.apache.org/jira/browse/HBASE-2248?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12845554#action_12845554
]
Todd Lipcon commented on HBASE-2248:
------------------------------------
Hey Ryan.
Will try to take a look at your patch early this week. Regarding the new
atomicity properties, can you please comment in HBASE-2294? I want to make sure
that, if we add these properties, that (a) they are really user requirements
and (b) we have documented them somewhere. If (a) isn't true, we should
document that, in case we find efficiency improvements we can make by dropping
some of them.
> Provide new non-copy mechanism to assure atomic reads in get and scan
> ---------------------------------------------------------------------
>
> Key: HBASE-2248
> URL: https://issues.apache.org/jira/browse/HBASE-2248
> Project: Hadoop HBase
> Issue Type: Bug
> Affects Versions: 0.20.3
> Reporter: Dave Latham
> Priority: Blocker
> Fix For: 0.20.4
>
> Attachments: HBASE-2248-demonstrate-previous-impl-bugs.patch,
> HBASE-2248-GetsAsScans3.patch, HBASE-2248-rr-alpha1.txt,
> HBASE-2248-ryan.patch, hbase-2248.gc, HBASE-2248.patch, hbase-2248.txt,
> readownwrites-lost.2.patch, readownwrites-lost.patch, Screen shot 2010-02-23
> at 10.33.38 AM.png, threads.txt
>
>
> HBASE-2037 introduced a new MemStoreScanner which triggers a
> ConcurrentSkipListMap.buildFromSorted clone of the memstore and snapshot when
> starting a scan.
> After upgrading to 0.20.3, we noticed a big slowdown in our use of short
> scans. Some of our data repesent a time series. The data is stored in time
> series order, MR jobs often insert/update new data at the end of the series,
> and queries usually have to pick up some or all of the series. These are
> often scans of 0-100 rows at a time. To load one page, we'll observe about
> 20 such scans being triggered concurrently, and they take 2 seconds to
> complete. Doing a thread dump of a region server shows many threads in
> ConcurrentSkipListMap.biuldFromSorted which traverses the entire map of key
> values to copy it.
--
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.
