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From "Karan Mehta (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-18097) Client can save 1 RPC call for CloseScannerRequest
Date Mon, 29 May 2017 23:24:04 GMT

    [ https://issues.apache.org/jira/browse/HBASE-18097?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16028663#comment-16028663
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Karan Mehta commented on HBASE-18097:
-------------------------------------

The first part for saving 1 RPC request is already implemented as a part of HBASE-17508, where
the scannerId is set to -1 whenever results are not left in region. 
For the second part related to ScanResponse proto, we can save some data in RPC call. 
[~Apache9] Do you feel it is reasonable to do so from the next version?

> Client can save 1 RPC call for CloseScannerRequest
> --------------------------------------------------
>
>                 Key: HBASE-18097
>                 URL: https://issues.apache.org/jira/browse/HBASE-18097
>             Project: HBase
>          Issue Type: Improvement
>            Reporter: Karan Mehta
>
> Starting version 1.3, HBase automatically closes scanner on server side whenever the
results are exhausted and corresponding bits are set in the {{ScanResponse}} proto returned
to the client. We can use that info to eliminate the closeScanRequest RPC call, thereby saving
1 RPC per region per scan. This can be particularly useful for tables with more regions.
> Also, currently the {{ScanResponse}} proto sends out 1 bit per {{Result}} that it has
embeds inside the {{CellScanner}} to indicate if it is partial or not. 
> {code}
>     // In every RPC response there should be at most a single partial result. Furthermore,
if
>     // there is a partial result, it is guaranteed to be in the last position of the
array.
> {code}
> According to client, only the last result can be partial, thus this repeated bool can
be converted to a bool, thus reducing overhead of serialization and deserialization of the
array. This will break wire compatibility therefore this is something to look for in upcoming
versions.



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