Change how we do meta tables; from tablename+STARTROW+randomid to instead,
tablename+ENDROW+randomid
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Key: HBASE-2600
URL: https://issues.apache.org/jira/browse/HBASE-2600
Project: Hadoop HBase
Issue Type: Improvement
Reporter: stack
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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