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From "Matt Corgan (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HBASE-7660) Remove HFileV1 code
Date Thu, 24 Jan 2013 22:09:13 GMT
Matt Corgan created HBASE-7660:
----------------------------------

             Summary: 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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