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https://issues.apache.org/jira/browse/HBASE-2600?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13188795#comment-13188795
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Lars Hofhansl edited comment on HBASE-2600 at 1/18/12 11:17 PM:
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@Alex: What is the problem with TestMetaMigrationRemovingHTD? The tar file with
that version of HBase is in ./src/test/data/hbase-4388-root.dir.tgz.
I am actually not sure what it means if that test fails.
@Stack: That seems to be the last stumbling block to get a successful test run.
I assume this test failing indicates something bad (that we cannot migrate meta
with this patch applied).
was (Author: lhofhansl):
@Alex: What the problem with TestMetaMigrationRemovingHTD? The tar file
with that version of HBase is in ./src/test/data/hbase-4388-root.dir.tgz.
I am actually not sure what it means if that test fails.
@Stack: That seems to be the last stumbling block to get a successful test run.
I assume this test failing indicates something bad (that we cannot migrate meta
with this patch applied).
> Change how we do meta tables; from tablename+STARTROW+randomid to instead,
> tablename+ENDROW+randomid
> ----------------------------------------------------------------------------------------------------
>
> Key: HBASE-2600
> URL: https://issues.apache.org/jira/browse/HBASE-2600
> Project: HBase
> Issue Type: Bug
> Reporter: stack
> Assignee: Alex Newman
> Attachments:
> 0001-Changed-regioninfo-format-to-use-endKey-instead-of-s.patch,
> 0001-HBASE-2600.-Change-how-we-do-meta-tables-from-tablen-v2.patch,
> 0001-HBASE-2600.-Change-how-we-do-meta-tables-from-tablen-v4.patch,
> 0001-HBASE-2600.-Change-how-we-do-meta-tables-from-tablen-v6.patch,
> 0001-HBASE-2600.-Change-how-we-do-meta-tables-from-tablen-v7.2.patch,
> 0001-HBASE-2600.-Change-how-we-do-meta-tables-from-tablen-v8,
> 0001-HBASE-2600.-Change-how-we-do-meta-tables-from-tablen-v8.1,
> 0001-HBASE-2600.-Change-how-we-do-meta-tables-from-tablen-v9.patch,
> 0001-HBASE-2600.-Change-how-we-do-meta-tables-from-tablen.patch,
> 2600-trunk-01-17.txt, jenkins.pdf
>
>
> This is an idea that Ryan and I have been kicking around on and off for a
> while now.
> If regionnames were made of tablename+endrow instead of tablename+startrow,
> then in the metatables, doing a search for the region that contains the
> wanted row, we'd just have to open a scanner using passed row and the first
> row found by the scan would be that of the region we need (If offlined
> parent, we'd have to scan to the next row).
> If we redid the meta tables in this format, we'd be using an access that is
> natural to hbase, a scan as opposed to the perverse, expensive
> getClosestRowBefore we currently have that has to walk backward in meta
> finding a containing region.
> This issue is about changing the way we name regions.
> If we were using scans, prewarming client cache would be near costless (as
> opposed to what we'll currently have to do which is first a
> getClosestRowBefore and then a scan from the closestrowbefore forward).
> Converting to the new method, we'd have to run a migration on startup
> changing the content in meta.
> Up to this, the randomid component of a region name has been the timestamp of
> region creation. HBASE-2531 "32-bit encoding of regionnames waaaaaaayyyyy
> too susceptible to hash clashes" proposes changing the randomid so that it
> contains actual name of the directory in the filesystem that hosts the
> region. If we had this in place, I think it would help with the migration to
> this new way of doing the meta because as is, the region name in fs is a hash
> of regionname... changing the format of the regionname would mean we generate
> a different hash... so we'd need hbase-2531 to be in place before we could do
> this change.
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