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From "jiraposter@reviews.apache.org (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-2600) Change how we do meta tables; from tablename+STARTROW+randomid to instead, tablename+ENDROW+randomid
Date Tue, 13 Dec 2011 23:23:30 GMT

    [ https://issues.apache.org/jira/browse/HBASE-2600?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13168847#comment-13168847
] 

jiraposter@reviews.apache.org commented on HBASE-2600:
------------------------------------------------------



bq.  On 2011-12-13 23:12:20, Ted Yu wrote:
bq.  > src/main/java/org/apache/hadoop/hbase/KeyValue.java, line 68
bq.  > <https://reviews.apache.org/r/3186/diff/2/?file=64439#file64439line68>
bq.  >
bq.  >     According to http://kickjava.com/src/java/util/UUID.java.htm, UUID.nameUUIDFromBytes()
resorts to MD5 MessageDigest.
bq.  >     
bq.  >     From http://www.docjar.com/html/api/java/security/MessageDigest.java.html, I
don't see machine name or time being involved.

Thanks Ted.  Yeah, saw that when went to read up on it.  Was going to suggest we just md5
it altogether but could go either way (and not important at this stage anyways).


- Michael


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On 2011-12-13 21:12:33, Alex Newman wrote:
bq.  
bq.  -----------------------------------------------------------
bq.  This is an automatically generated e-mail. To reply, visit:
bq.  https://reviews.apache.org/r/3186/
bq.  -----------------------------------------------------------
bq.  
bq.  (Updated 2011-12-13 21:12:33)
bq.  
bq.  
bq.  Review request for hbase.
bq.  
bq.  
bq.  Summary
bq.  -------
bq.  
bq.  PART 1 of hbase-4616
bq.  
bq.  This is an idea that Ryan and I have been kicking around on and off for a while now.
bq.  
bq.  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).
bq.  
bq.  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.
bq.  
bq.  This issue is about changing the way we name regions.
bq.  
bq.  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).
bq.  
bq.  Converting to the new method, we'd have to run a migration on startup changing the content
in meta.
bq.  
bq.  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.
bq.  
bq.  
bq.  This addresses bug HBASE-2600.
bq.      https://issues.apache.org/jira/browse/HBASE-2600
bq.  
bq.  
bq.  Diffs
bq.  -----
bq.  
bq.    src/main/java/org/apache/hadoop/hbase/HConstants.java 1cf58a9 
bq.    src/main/java/org/apache/hadoop/hbase/HRegionInfo.java 74cb821 
bq.    src/main/java/org/apache/hadoop/hbase/KeyValue.java be7e2d8 
bq.    src/main/java/org/apache/hadoop/hbase/catalog/MetaReader.java e5e60a8 
bq.    src/main/java/org/apache/hadoop/hbase/client/HBaseAdmin.java 6bff130 
bq.    src/main/java/org/apache/hadoop/hbase/client/HConnectionManager.java 6f19d21 
bq.    src/main/java/org/apache/hadoop/hbase/client/MetaScanner.java 4135e55 
bq.    src/main/java/org/apache/hadoop/hbase/client/MetaSearchRow.java PRE-CREATION 
bq.    src/main/java/org/apache/hadoop/hbase/rest/RegionsResource.java bf85bc1 
bq.    src/main/java/org/apache/hadoop/hbase/rest/model/TableRegionModel.java 67e7a04 
bq.    src/test/java/org/apache/hadoop/hbase/HBaseTestingUtility.java 6fca020 
bq.    src/test/java/org/apache/hadoop/hbase/TestKeyValue.java dc4ee8d 
bq.    src/test/java/org/apache/hadoop/hbase/client/TestAdmin.java 95712dd 
bq.    src/test/java/org/apache/hadoop/hbase/regionserver/TestGetClosestAtOrBefore.java 5f97167

bq.    src/test/java/org/apache/hadoop/hbase/regionserver/TestHRegionInfo.java 6e1211b 
bq.    src/test/java/org/apache/hadoop/hbase/regionserver/TestMemStore.java a092cf0 
bq.    src/test/java/org/apache/hadoop/hbase/regionserver/TestSplitTransactionOnCluster.java
1997abd 
bq.    src/test/java/org/apache/hadoop/hbase/rest/model/TestTableRegionModel.java b6f0ab5

bq.  
bq.  Diff: https://reviews.apache.org/r/3186/diff
bq.  
bq.  
bq.  Testing
bq.  -------
bq.  
bq.  
bq.  Thanks,
bq.  
bq.  Alex
bq.  
bq.


                
> 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: Sub-task
>            Reporter: stack
>            Assignee: Alex Newman
>         Attachments: 0001-Changed-regioninfo-format-to-use-endKey-instead-of-s.patch
>
>
> 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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