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From "Ted Yu (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-7660) Remove HFileV1 code
Date Sat, 26 Jan 2013 22:37:12 GMT

    [ https://issues.apache.org/jira/browse/HBASE-7660?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13563666#comment-13563666
] 

Ted Yu commented on HBASE-7660:
-------------------------------

Looking at HFile.Reader, most methods don't have javadoc, leaving interpretation of the interface
to each developer.

In the process of creating Cell interface, we have avoided such mistake.

bq. put it in something like hbase-support/hfile-v1-to-v2-tool that can be used as migration
tool?
Some users are using 0.94.x and to my knowledge, there was no request for creating migration
tool.
                
> Remove HFileV1 code
> -------------------
>
>                 Key: HBASE-7660
>                 URL: https://issues.apache.org/jira/browse/HBASE-7660
>             Project: HBase
>          Issue Type: Improvement
>          Components: hbck, HFile, migration
>            Reporter: Matt Corgan
>             Fix For: 0.96.0
>
>
> HFileV1 should be removed from the regionserver because it is somewhat of a drag on development
for working on the lower level read paths.  It's an impediment to cleaning up the Store code.
> V1 HFiles ceased to be written in 0.92, but the V1 reader was left in place so users
could upgrade from 0.90 to 0.92.  Once all HFiles are compacted in 0.92, then the V1 code
is no longer needed.  We then decided to leave the V1 code in place in 0.94 so users could
upgrade directly from 0.90 to 0.94.  The code is still there in trunk but should probably
be shown the door.  I see a few options:
> 1) just delete the code and tell people to make sure they compact everything using 0.92
or 0.94
> 2) create a standalone script that people can run on their 0.92 or 0.94 cluster that
iterates the filesystem and prints out any v1 files with a message that the user should run
a major compaction
> 3) add functionality to 0.96.0 (first release, maybe in hbck) that proactively kills
v1 files, so that we can be sure there are none when upgrading from 0.96 to 0.98
> 4) punt to 0.98 and probably do one of the above options in a year
> I would vote for #1 or #2 which will allow us to have a v1-free 0.96.0.  HFileV1 has
already survived 2 major release upgrades which i think many would agree is more than enough
for a pre-1.0, free product.  If we can remove it in 0.96.0 it will be out of the way to introduce
some nice performance improvements in subsequent 0.96.x releases.

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