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https://issues.apache.org/jira/browse/PHOENIX-5688?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Lars Hofhansl updated PHOENIX-5688:
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Summary: Investigate better client/server work pacing (was: Investigate
better server work pacing)
> Investigate better client/server work pacing
> --------------------------------------------
>
> Key: PHOENIX-5688
> URL: https://issues.apache.org/jira/browse/PHOENIX-5688
> Project: Phoenix
> Issue Type: Bug
> Reporter: Lars Hofhansl
> Priority: Major
>
> [~kozdemir] shared an intriguing idea that he used for the server side index
> repair tool, which would equally well apply to the server side deletes and
> server side UPSERT/SELECT.
> The main problem with the current implementation is that we basically send a
> predicate to the server - DELETE FROM <table> WHERE <condition>. Now the
> server(s) will go away per region chunk, evaluate the condition and delete
> whatever matched it... All in tight server loop.
> The downside is that (a) a server thread is held up arbitrarily long, (b)
> there is no way for the server to do any fair queuing, the loop has to
> finish, and (c) if the server takes too long the client will just time out.
> The alternative used to be to do the work on the client instead: Issue a scan
> with the condition to the server, retrieve the IDs to the client, and then
> issue nice chunks of deletes back to the server.
> The downside here is the extra communication overhead between the server and
> client (which might be especially taxing for UPSERT/SELECTS).
> Kadir's approach is a middle ground:
> # Issue a scan from the client, and send along a chunk size (N rows), when
> getting the scanner.
> # The server will do N rows worth of work, then return.
> # The client keeps the scanner open, and calls next.
> # Goto #2
> This way we get the benefit of both approaches: (1) work close to where the
> data is, (2) the client can pace the work and the server gets a chance to
> schedule other work.
>
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