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From "Nick Dimiduk (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-11331) [blockcache] lazy block decompression
Date Fri, 13 Jun 2014 19:03:02 GMT

    [ https://issues.apache.org/jira/browse/HBASE-11331?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14031006#comment-14031006
] 

Nick Dimiduk commented on HBASE-11331:
--------------------------------------

Decompressed blocks aren't stored anywhere in the patch posted. This patch, just as current
master code, decompressed an HFileBlock into an on-heap ByteBuffer. There's no additional
cache layer for decompressed blocks as it stands currently; they're decompressed, consumed,
and thrown away. HFileReaderV2$AbstractScannerV2 keeps a reference to the current block, so
a single GET shouldn't pay the cost of decompression multiple times, but I need to confirm
this is true.

> [blockcache] lazy block decompression
> -------------------------------------
>
>                 Key: HBASE-11331
>                 URL: https://issues.apache.org/jira/browse/HBASE-11331
>             Project: HBase
>          Issue Type: Improvement
>          Components: regionserver
>            Reporter: Nick Dimiduk
>            Assignee: Nick Dimiduk
>         Attachments: HBASE-11331.00.patch
>
>
> Maintaining data in its compressed form in the block cache will greatly increase our
effective blockcache size and should show a meaning improvement in cache hit rates in well
designed applications. The idea here is to lazily decompress/decrypt blocks when they're consumed,
rather than as soon as they're pulled off of disk.
> This is related to but less invasive than HBASE-8894.



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