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https://issues.apache.org/jira/browse/HBASE-17339?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15790072#comment-15790072
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Eshcar Hillel commented on HBASE-17339:
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[~stack] I see the scheme described in HBASE-10247.
I think it is better to explicitly run the test for monotonically increasing ts
rather than rely on a configuration setting.
First ,the application can always violate its guarantee either due to a bug at
the application level or due to lack of understanding of the property. So if we
run the test we guard the application from itself.
Second, the test itself does not cost much. Simply ask all stores in the region
if they maintain this property. This is a memory-only computation, no IO
involved.
Once TS_policy is in and generally well understood by users, we can use it to
replace the explicit test.
> Scan-Memory-First Optimization for Get Operation
> ------------------------------------------------
>
> 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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