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From ameet kini <>
Subject Re: number of query threads for batch scanner
Date Tue, 25 Sep 2012 18:45:51 GMT
Probably worth adding that the table mentioned below has a bunch of tablets
on other tablet servers as well, which is why I'm using BatchScanner. I'm
just not sure how the numQueryThreads relates to the number of a concurrent
scans on a given tablet server.


On Tue, Sep 25, 2012 at 2:22 PM, ameet kini <> wrote:

> I have a table with 4 tablets on a given tablet server. Depending on the
> numQueryThreads parameter below, I see a varying number of maximum
> concurrent scans on that table. This maximum number varies from 1 to 3
> (i.e., some values for numQueryThreads result in maximum concurrent scan of
> 1, some values result in 2 concurrent scans, etc.). Can someone shed light
> on what is the relationship between numQueryThreads and number of
> concurrent scans?
> public BatchScanner createBatchScanner(String tableName,
>                                        Authorizations authorizations,
>                                        int numQueryThreads)
> A follow-on question would be what is general rule of thumb for setting
> numQueryThreads? Should it be set to the  # of hosted tablets expected to
> be consumed by that BatchScanner? Should it be the # of tablet servers
> expected to be hit by that BatchScanner? Something else?
> Thanks,
> Ameet

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