[jira] [Commented] (KUDU-1704) Add a new read mode to perform bounded staleness snapshot reads

["Alexey Serbin (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/KUDU-1704?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15685765#comment-15685765 ] 

Alexey Serbin commented on KUDU-1704:
-------------------------------------

A couple of questions to clarify:

For the new scan mode, it might make sense to have the following semantics for scan timestamp:
* explicitly specified: in the corresponding tablet, select server's first operation which happens after the specified timestamp
* not specified/omitted: in the corresponding tablet, select server's latest committed operation

Also, there is a question: what timestamp do we choose if the first tablet server contacted among those hosting the tablet does not have any committed operations yet?

> Add a new read mode to perform bounded staleness snapshot reads
> ---------------------------------------------------------------
>
>                 Key: KUDU-1704
>                 URL: https://issues.apache.org/jira/browse/KUDU-1704
>             Project: Kudu
>          Issue Type: Sub-task
>    Affects Versions: 1.1.0
>            Reporter: David Alves
>            Assignee: Alexey Serbin
>
> It would be useful to be able to perform snapshot reads at a timestamp that is higher than a client provided timestamp, thus improving recency, but lower that the server's oldest inflight transaction, thus minimizing the scan's chance to block.
> Such a mode would not guarantee linearizability, but would still allow for client-local read-your-writes, which seems to be one of the properties users care about the most.
> This should likely be the new default read mode for scanners.



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