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From "ramkrishna.s.vasudevan (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-16372) References to previous cell in read path should be avoided
Date Fri, 19 Aug 2016 12:01:20 GMT

    [ https://issues.apache.org/jira/browse/HBASE-16372?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15428058#comment-15428058
] 

ramkrishna.s.vasudevan commented on HBASE-16372:
------------------------------------------------

One thing is handling it in the lower levels like the HFileReader level is very tricky but
the StoreScanner layer is in a way better. Atleast we know why we take references and in what
scenario the references are not updated to the actual last Cell. 

> References to previous cell in read path should be avoided
> ----------------------------------------------------------
>
>                 Key: HBASE-16372
>                 URL: https://issues.apache.org/jira/browse/HBASE-16372
>             Project: HBase
>          Issue Type: Sub-task
>          Components: Scanners
>    Affects Versions: 2.0.0
>            Reporter: ramkrishna.s.vasudevan
>            Assignee: ramkrishna.s.vasudevan
>            Priority: Critical
>             Fix For: 2.0.0
>
>         Attachments: HBASE-16372_testcase.patch, HBASE-16372_testcase_1.patch
>
>
> Came as part of review discussion in HBASE-15554. If there are references kept to previous
cells in the read path, with the Ref count based eviction mechanism in trunk, then chances
are there to evict a block backing the previous cell but the read path still does some operations
on that garbage collected previous cell leading to incorrect results.
> Areas to target
> -> Storescanner
> -> Bloom filters (particularly in compaction path)
> Thanks to [~anoop.hbase] to point out this in bloomfilter path. But we found it could
be in other areas also.



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