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https://issues.apache.org/jira/browse/HBASE-2600?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13444349#comment-13444349
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Matt Corgan commented on HBASE-2600:
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{quote}\x00 could be part of a region key but the sort on table name first
should make it so the \x00 delimiter would be found first{quote}yep - in
general, this is how i build compound primary keys with variable length
strings. you shouldn't need any padding or anything. the only complication is
if your string somehow contains \x00, but that can't happen in this case
As for moving the regionId to the qualifier, I don't really know enough about
how it's used to give detailed ideas, but some thoughts:
* there will not be many daughter regions at a given time, so we are not
talking about wide rows
* perhaps putting the daughters into the same row adds some transactional
benefits that we didn't previously have?
* as for qualifier-prefix vs separate-qualifier, i actually don't know enough
about usage to say if neither/either/both would work. seems like either could
work given that each row will be small enough to easily hold in memory and
parse however. i first proposed prefixing to keep the KV sort order intact,
but if that isn't required then separate-qualifier is cleaner.
> 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.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.v10.patch, 0001-HBASE-2600-v11.patch, 2600-trunk-01-17.txt,
> HBASE-2600+5217-Sun-Mar-25-2012-v3.patch,
> HBASE-2600+5217-Sun-Mar-25-2012-v4.patch, hbase-2600-root.dir.tgz, 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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