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From "Eshcar Hillel (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-19095) Add CP hooks in RegionObserver for in memory compaction
Date Sun, 29 Oct 2017 19:51:00 GMT

    [ https://issues.apache.org/jira/browse/HBASE-19095?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16224169#comment-16224169

Eshcar Hillel commented on HBASE-19095:

Basic mode does not use StoreScanner. Basic applies two kinds of steps - a flattening step
and a merge step.
A merge step creates a MemStoreMergerSegmentsIterator. This iterator manages a KeyValueHeap
it uses it to merge the index of several segments, and does not drop any cell. 
A flattening step simply uses a segment scanner to create a flat index, and does not drop
any cell.
I would not open these to CP hooks.

Other modes (like Eager, and Adaptive which I am about to commit to trunk) may apply a compact
step which imitates disk data compaction in-memory.
A compact step creates a MemStoreCompactorSegmentsIterator which uses a StoreScanner as described
Here, I agree there is room to give the user control on the number of versions to keep, TTL

> Add CP hooks in RegionObserver for in memory compaction
> -------------------------------------------------------
>                 Key: HBASE-19095
>                 URL: https://issues.apache.org/jira/browse/HBASE-19095
>             Project: HBase
>          Issue Type: Sub-task
>          Components: Coprocessors
>            Reporter: Duo Zhang
>             Fix For: 2.0.0-beta-1
> This is a hole in our CP hooks.

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