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From "Vladimir Rodionov (JIRA)" <j...@apache.org>
Subject [jira] [Comment Edited] (HBASE-17339) Scan-Memory-First Optimization
Date Mon, 19 Dec 2016 20:09:58 GMT

    [ https://issues.apache.org/jira/browse/HBASE-17339?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15762163#comment-15762163
] 

Vladimir Rodionov edited comment on HBASE-17339 at 12/19/16 8:09 PM:
---------------------------------------------------------------------

This won't work in a general case.

You may have KV in Memory and in store files (different versions). HBase does not give you
a guarantee, that memory version is what you ask for (unless you specify exact version).

This can be used only as a hint: If KV is memory give it to me, or MEMSTORE_FIRST.



was (Author: vrodionov):
This won't work in a general case.

You may have KV in Memory and in store files (different versions). HBase does not give you
a guarantee, that memory version is what you ask for (unless you specify exact version).

This can be used only as a hint: If KV is memory give it to me, or MESTORE_FIRST.


> Scan-Memory-First Optimization
> ------------------------------
>
>                 Key: HBASE-17339
>                 URL: https://issues.apache.org/jira/browse/HBASE-17339
>             Project: HBase
>          Issue Type: Improvement
>            Reporter: Eshcar Hillel
>         Attachments: HBASE-17339-V01.patch
>
>
> The current implementation of a get operation (to retrieve values for a specific key)
scans through all relevant stores of the region; for each store both memory components (memstores
segments) and disk components (hfiles) are scanned in parallel.
> We suggest to apply an optimization that speculatively scans memory-only components first
and only if the result is incomplete scans both memory and disk.



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