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https://issues.apache.org/jira/browse/PHOENIX-1751?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15432236#comment-15432236
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James Taylor commented on PHOENIX-1751:
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I seem to remember Lars mentioning that if you did work in preScannerOpen
instead of postScannerOpen, the lease wouldn't expire, but perhaps I got that
wrong. What do you think, [~lhofhansl]?
> Perform aggregations, sorting, etc, in the preScannerOpen instead of
> postScannerOpen
> ------------------------------------------------------------------------------------
>
> Key: PHOENIX-1751
> URL: https://issues.apache.org/jira/browse/PHOENIX-1751
> Project: Phoenix
> Issue Type: Bug
> Reporter: Lars Hofhansl
> Assignee: James Taylor
> Attachments: 1751-WIP-v2.txt, 1751-WIP-v2b.patch, 1751-WIP.txt,
> PHOENIX-1751-v2c.patch, PHOENIX-1751.patch, PHOENIX-1751_v3.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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