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.
- 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