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https://issues.apache.org/jira/browse/HBASE-9272?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13748853#comment-13748853
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Lars Hofhansl commented on HBASE-9272:
--------------------------------------
Some more data:
30m rows, 2 CFs, 5 columns each, with 100 bytes values. Split into 128 regions
When all data is returned - this is limited by what the client can consume (via
the network and by actually iterating over the result). All numbers in seconds:
||ClientScanner||1 thread||2 threads||5 threads||10 threads||50 threads||
|519|529|303|192|189|187|
When all is filtered with a ValueFilter on the server (as in an analytics
query):
||ClientScanner||1 thread||5 threads||10 threads||50 threads||
|53.3|53.3|28.4|11.6|6.42|1.88|
> A simple parallel, unordered scanner
> ------------------------------------
>
> Key: HBASE-9272
> URL: https://issues.apache.org/jira/browse/HBASE-9272
> Project: HBase
> Issue Type: New Feature
> Reporter: Lars Hofhansl
> Assignee: Lars Hofhansl
> Priority: Minor
> Attachments: ParallelClientScanner.java, ParallelClientScanner.java
>
>
> The contract of ClientScanner is to return rows in sort order. That limits
> the order in which region can be scanned.
> I propose a simple ParallelScanner that does not have this requirement and
> queries regions in parallel, return whatever gets returned first.
> This is generally useful for scans that filter a lot of data on the server,
> or in cases where the client can very quickly react to the returned data.
> I have a simple prototype (doesn't do error handling right, and might be a
> bit heavy on the synchronization side - it used a BlockingQueue to hand data
> between the client using the scanner and the threads doing the scanning, it
> also could potentially starve some scanners long enugh to time out at the
> server).
> On the plus side, it's only a 130 lines of code. :)
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