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https://issues.apache.org/jira/browse/HBASE-18055?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16011824#comment-16011824
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Duo Zhang commented on HBASE-18055:
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Pardon me, I do not understand what is going on here.
You mean that the newly created scanner will reference to a block whose ref
count is 0 so we may get incorrect result?
> HBASE-17917 closes the scanners while a scan is in progess for switching over
> to stream reads
> ---------------------------------------------------------------------------------------------
>
> Key: HBASE-18055
> URL: https://issues.apache.org/jira/browse/HBASE-18055
> Project: HBase
> Issue Type: Bug
> Components: regionserver, Scanners
> Affects Versions: 2.0.0
> Reporter: ramkrishna.s.vasudevan
> Assignee: ramkrishna.s.vasudevan
> Fix For: 2.0.0
>
>
> In HBASE-17917 tries to switch from pread to stream read when a specific size
> of bytes are read. So in order to switch over, it closes the existing
> scanners and creates a new scanners with pread=false.
> When we close the exisitng scanners - if the blocks are served from offheap
> cache we will decrement the ref count on those blocks and if it becomes zero
> we make the block ready for eviction. Then there is a chance that the result
> could be corrupted if new blocks occupy the cache. So the expectation was
> that till the RPC call completes the response we will hold on to the blocks
> that are referred by the scan. (except the last one). So trying to switch
> over to stream read will break this expectation and hence
> TestBlockEvictionfromclient fails.
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