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https://issues.apache.org/jira/browse/PHOENIX-1751?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15423876#comment-15423876
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James Taylor commented on PHOENIX-1751:
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It looks like we always do the bulk of the work in postScannerOpen (which can
lead to lease expiration exceptions if it takes longer than the lease period).
I think one easy fix would be to do all the work in preScannerOpen (which
handles lease expiration by renewing it when complete). We just have to ensure
that the first resultSet.next() is the thing that triggers the scanner open and
first next call (which I think it may do already).
> 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
> Attachments: 1751-WIP-v2.txt, 1751-WIP-v2b.patch, 1751-WIP.txt,
> PHOENIX-1751-v2c.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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