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From "stack (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-15359) Simplifying Segment hierarchy
Date Mon, 29 Feb 2016 18:39:18 GMT

    [ https://issues.apache.org/jira/browse/HBASE-15359?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15172329#comment-15172329

stack commented on HBASE-15359:

bq. Now that it is clear that no memstore segment will be implemented as an HFIle....

Where does the above assertion come from [~eshcar]?

Thanks for doing this cleanup if above is true.

Why rollback? We don't need it anymore since HBASE-12751 and reorder of write pipeline so
edit is in sync'd and in WAL before we add to memstore.

Otherwise, patch looks great.

> Simplifying Segment hierarchy
> -----------------------------
>                 Key: HBASE-15359
>                 URL: https://issues.apache.org/jira/browse/HBASE-15359
>             Project: HBase
>          Issue Type: Sub-task
>            Reporter: Eshcar Hillel
>            Assignee: Eshcar Hillel
>             Fix For: 0.98.18
>         Attachments: HBASE-14918-FIX-SEGMENT.patch
> Now that it is clear that no memstore segment will be implemented as an HFIle, and that
all segments store their data in some representation of CellSet (skip-list or flat), the segment
hierarchy can be much simplified.
> The attached patch includes only 3 classes in the hierarchy:
> Segment - comprises most of the state and implementation
> MutableSegment - extends API with add and rollback functionality
> ImmutableSegment - extends API with key-value scanner for snapshot
> SegmentScanner is the scanner for all types of segments. 
> In addition, the option to rollback immutable segment in the memstore is disabled.
> This code would allow us to make progress independently in the compaction subtask (HBASE-14920)
and the flat index representation subtask (HBASE-14921). It also means that the new immutable
segment can reuse the existing SegmentScanner, instead of implementing a new scanner.

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