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From "Andrew Purtell (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (PHOENIX-1751) Perform aggregations, sorting, etc, in the preScannerNext instead of postScannerOpen
Date Thu, 25 Aug 2016 01:08:20 GMT

    [ https://issues.apache.org/jira/browse/PHOENIX-1751?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15436071#comment-15436071
] 

Andrew Purtell commented on PHOENIX-1751:
-----------------------------------------

Ok, then I don't have a good idea what the issue might be

> Perform aggregations, sorting, etc, in the preScannerNext instead of postScannerOpen
> ------------------------------------------------------------------------------------
>
>                 Key: PHOENIX-1751
>                 URL: https://issues.apache.org/jira/browse/PHOENIX-1751
>             Project: Phoenix
>          Issue Type: Bug
>            Reporter: Lars Hofhansl
>            Assignee: Lars Hofhansl
>         Attachments: 1751-WIP-v2.txt, 1751-WIP-v2b.patch, 1751-WIP.txt, PHOENIX-1751-0.98.patch,
PHOENIX-1751-v2c.patch, PHOENIX-1751.patch, PHOENIX-1751_v3.patch, PHOENIX-1751_v4.patch
>
>
> HBase retains a lease for every scanner. Then lease expires the scan will no longer (be
allowed to) work. The leases guard against the client going away, and allow cleaning up resources
if that happens.
> At various points HBase "suspends" the lease while the region server are working on behalf
of this scanner, so that the lease won't expire even though the server is working on it.
> HBase does that during the scanning process. Crucially it suspends the leaser after the
scanner is opened, before next() is issued on it.
> The outcome of all this is that Phoenix executes aggregates, sorts, etc, with the lease
in place, and hence if these take a bit the lease can expire even though the server was working
on it.
> Phoenix should do this work in preScannerNext, being careful that the precalculation
is only performed once.
> I'll attach a sample patch soon.



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