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From "George P. Stathis (JIRA)" <j...@apache.org>
Subject [jira] Created: (HBASE-2426) [Transactional Contrib] Introduce quick scanning row-based secondary indexes
Date Thu, 08 Apr 2010 16:10:38 GMT
[Transactional Contrib] Introduce quick scanning row-based secondary indexes
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                 Key: HBASE-2426
                 URL: https://issues.apache.org/jira/browse/HBASE-2426
             Project: Hadoop HBase
          Issue Type: New Feature
          Components: contrib
            Reporter: George P. Stathis
            Priority: Minor
             Fix For: 0.20.5, 0.21.0


RowBasedIndexSpecification is a specialized IndexSpecification class for creating row-based
secondary index tables. Base table rows with the same indexed column value have their row
keys stored as column qualifiers on the same secondary index table row. The key for that row
is the indexed column value from the base table. This allows to avoid expensive secondary
index table scans and provides faster access for applications such as foreign key indexing
or queries such as "find all table A rows whose familyA:columnB value is X". RowBasedIndexSpecification
indices can be scanned using the API on RowBasedIndexedTable. The metadata for RowBasedIndexSpecification
differ from IndexSpecification in that:

- Only a single base table column can be indexed per RowBasedIndexSpecification. No additional
columns are put in the index table.
and 
- RowBasedIndexKeyGenerator, which constructs the index-row-key from the indexed column value
in the original column, is always used.

For a simple RowBasedIndexSpecification example, look at the TestRowBasedIndexedTable unit
test in org.apache.hadoop.hbase.client.tableIndexed.

To enable RowBasedIndexSpecification indexing, modify hbase-site.xml to turn on the
IndexedRegionServer.  This is done by setting
- hbase.regionserver.class to org.apache.hadoop.hbase.ipc.IndexedRegionInterface and
- hbase.regionserver.impl to org.apache.hadoop.hbase.regionserver.tableindexed.RowBasedIndexedRegionServer

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