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https://issues.apache.org/jira/browse/HBASE-9272?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13790012#comment-13790012
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stack commented on HBASE-9272:
------------------------------
Looks great. +1
Minor stuff to address on commit.
nit: try/finally for this bit
+ List<HRegionLocation> locs = t.getRegionsInRange(scan.getStartRow(),
scan.getStopRow());
+ t.close();
nit: presize + Map<HRegionLocation, Queue<Scan>> tasks = new
HashMap<HRegionLocation, Queue<Scan>>(); -- you know how many regions
nit: + * doesn't wait until the threapool actually closes -- spelling
You mean volatile here? + private transient double parallelScaling = 0;
Agree it should be in HTable. I like addtion to the shell.
'Task' is too generic a name for the class and the ReaderWriter looks like a
Queue but as long as these classes are kept private should be fine.
MyResult is a bit hokey for a class name. Done or DoneMarker? Bit more doc
on its operation (it makes sense when you take a look but not reading the class
alone).
> 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: 9272-0.94.txt, 9272-0.94-v2.txt, 9272-0.94-v3.txt,
> 9272-0.94-v4.txt, 9272-trunk.txt, 9272-trunk-v2.txt,
> 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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