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From "Anoop Sam John (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-15325) ResultScanner allowing partial result will miss the rest of the row if the region is moved between two rpc requests
Date Wed, 09 Mar 2016 06:48:41 GMT

    [ https://issues.apache.org/jira/browse/HBASE-15325?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15186624#comment-15186624
] 

Anoop Sam John commented on HBASE-15325:
----------------------------------------

Ya there will be only client side change
- When a batch limit is NOT set on the scan, we will see whether the last fetched Result is
a partial one. If so we will start with that row in the next scanner. If not the start row
of the new scanner will be next row(as in current code). Also we will skip the cells what
we already got. Or even we can clear the Results on this row what we have now
- When a batch is set on scan, we will treat always that we are at middle of the row. And
the new scanner will be having a start of row = this last row. Only exception is a short circuit
(to avoid fetching one more row) where we will make next row as new scanner start row, when
the last returned batch on this row is NOT partial but has lesser #cells than the batch size.
Here we are sure that this is the last possible batch.

> ResultScanner allowing partial result will miss the rest of the row if the region is
moved between two rpc requests
> -------------------------------------------------------------------------------------------------------------------
>
>                 Key: HBASE-15325
>                 URL: https://issues.apache.org/jira/browse/HBASE-15325
>             Project: HBase
>          Issue Type: Bug
>          Components: dataloss, Scanners
>    Affects Versions: 1.2.0, 1.1.3
>            Reporter: Phil Yang
>            Assignee: Phil Yang
>            Priority: Critical
>         Attachments: 15325-test.txt, HBASE-15325-v1.txt, HBASE-15325-v2.txt, HBASE-15325-v3.txt,
HBASE-15325-v5.txt, HBASE-15325-v6.1.txt, HBASE-15325-v6.2.txt, HBASE-15325-v6.3.txt, HBASE-15325-v6.4.txt,
HBASE-15325-v6.5.txt, HBASE-15325-v6.txt
>
>
> HBASE-11544 allow scan rpc return partial of a row to reduce memory usage for one rpc
request. And client can setAllowPartial or setBatch to get several cells in a row instead
of the whole row.
> However, the status of the scanner is saved on server and we need this to get the next
part if there is a partial result before. If we move the region to another RS, client will
get a NotServingRegionException and open a new scanner to the new RS which will be regarded
as a new scan from the end of this row. So the rest cells of the row of last result will be
missing.



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