[jira] [Commented] (HBASE-4241) Optimize flushing of the Store cache for max versions and (new) min versions

["Lars Hofhansl (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HBASE-4241?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13090420#comment-13090420 ] 

Lars Hofhansl commented on HBASE-4241:
--------------------------------------

Turns out this is actually most useful to avoid flushing versions past the maxversion to disk, and only somewhat related to HBASE-4071.
It's not that likely that TTL is so short that rows in the memstore expire before they are flushed to disk. however, there are scenarios (such as state or counter) tables where maxversions=1 and there bery frequent updates.

I have a test patch and testing with such a scnerio and found the disk saving are significant. I think this warrant a top-level jira. I'll close one.


> Optimize flushing of the Store cache for max versions and (new) min versions
> ----------------------------------------------------------------------------
>
>                 Key: HBASE-4241
>                 URL: https://issues.apache.org/jira/browse/HBASE-4241
>             Project: HBase
>          Issue Type: Sub-task
>          Components: regionserver
>    Affects Versions: 0.92.0
>            Reporter: Lars Hofhansl
>            Priority: Minor
>
> As discussed with with Jon, there is room for improvement in how the memstore is flushed to disk.
> Currently only expired KVs are pruned before flushing, but we can also prune versions if we find at least maxVersions versions in the memstore.
> The same holds for the new minversion feature: If we find at least minVersion versions in the store we can remove all further versions that are expired.
> Generally we should use the same mechanism here that is used for Compaction. I.e. StoreScanner. We only need to add a scanner to Memstore that can scan along the current snapshot.

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