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Date: Mon, 1 Oct 2012 04:00:07 +1100 (NCT)
From: "ramkrishna.s.vasudevan (JIRA)" <jira@apache.org>
To: issues@hbase.apache.org
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Subject: [jira] [Updated] (HBASE-6900) RegionScanner.reseek() creates NPE
 when a flush or compaction happens before the reseek.
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     [ https://issues.apache.org/jira/browse/HBASE-6900?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

ramkrishna.s.vasudevan updated HBASE-6900:
------------------------------------------

    Attachment: HBASE-6900_1.patch

Patch with fix.  I have not run testsuite yet.
The checkReseek() returns true if the heap is null.  So both checkReseek and null check is needed i feel.
Pls review and provide your comments/suggestions.
                
> RegionScanner.reseek() creates NPE when a flush or compaction happens before the reseek.
> ----------------------------------------------------------------------------------------
>
>                 Key: HBASE-6900
>                 URL: https://issues.apache.org/jira/browse/HBASE-6900
>             Project: HBase
>          Issue Type: Bug
>            Reporter: ramkrishna.s.vasudevan
>            Assignee: ramkrishna.s.vasudevan
>         Attachments: HBASE-6900_1.patch, HBASE-6900.patch
>
>
> HBASE-5520 introduced reseek() on the RegionScanner.  
> Now when a scanner is created we have the StoreScanner heap.  After this if a flush or compaction happens parallely all the StoreScannerObservers are cleared so that whenever a new next() call happens we tend to recreate the scanner based on the latest store files.
> The reseek() in StoreScanner expects the heap not to be null because always reseek would be called from next()
> {code}
> public synchronized boolean reseek(KeyValue kv) throws IOException {
>     //Heap cannot be null, because this is only called from next() which
>     //guarantees that heap will never be null before this call.
>     if (explicitColumnQuery && lazySeekEnabledGlobally) {
>       return heap.requestSeek(kv, true, useRowColBloom);
>     } else {
>       return heap.reseek(kv);
>     }
>   }
> {code}
> Now when we call RegionScanner.reseek() directly using CPs we tend to get a NPE.  In our case it happened when a major compaction was going on.  I will also attach a testcase to show the problem.

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