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From "ramkrishna.s.vasudevan (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-15398) Cells loss or disorder when using family essential filter and partial scanning protocol
Date Wed, 09 Mar 2016 04:59:41 GMT

    [ https://issues.apache.org/jira/browse/HBASE-15398?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15186502#comment-15186502
] 

ramkrishna.s.vasudevan commented on HBASE-15398:
------------------------------------------------

To start with (I may be wrong here reading this code now)
{code}
        if (this.filter == null || !scan.doLoadColumnFamiliesOnDemand()
          || this.filter.isFamilyEssential(entry.getKey())) {
          scanners.add(scanner);
        } else {
          joinedScanners.add(scanner);
        }
{code}
If there is a SCVF configured and scan says setLoadColumnFamiliesOnDemand(true) - we will
only have joinedHeap active on the RegionScanner? Then storeHeap is guarded enough not to
fetch results from it? And will the scan continue with joinedHeap? 

> Cells loss or disorder when using family essential filter and partial scanning protocol
> ---------------------------------------------------------------------------------------
>
>                 Key: HBASE-15398
>                 URL: https://issues.apache.org/jira/browse/HBASE-15398
>             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: 15398-test.txt, HBASE-15398.v1.txt
>
>
> In RegionScannerImpl, we have two heaps, storeHeap and joinedHeap. If we have a filter
and it doesn't apply to all cf, the stores whose families needn't be  filtered will be in
joinedHeap. We scan storeHeap first, then joinedHeap, and merge the results and sort and return
to client. We need sort because the order of Cell is rowkey/cf/cq/ts and a smaller cf may
be in the joinedHeap.
> However, after HBASE-11544 we may transfer partial results when we get SIZE_LIMIT_REACHED_MID_ROW
or other similar states. We may return a larger cf first because it is in storeHeap and then
a smaller cf because it is in joinedHeap. Server won't hold all cells in a row and client
doesn't have a sorting logic. The order of cf in Result for user is wrong.
> And a more critical bug is, if we get a LIMIT_REACHED_MID_ROW on the last cell of a row
in storeHeap, we will break scanning in RegionScannerImpl and in populateResult we will change
the state to SIZE_LIMIT_REACHED because next peeked cell is next row. But this is only the
last cell of one and we have two... And SIZE_LIMIT_REACHED means this Result is not partial
(by ScannerContext.partialResultFormed), client will see it and merge them and return to user
with losing data of joinedHeap. On next scan we will read next row of storeHeap and joinedHeap
is forgotten and never be read...



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