Getting Started

To start using Indexed HBase do the following:

1. Set the hbase.region.impl property to IdxRegion
   

   <property>
     <name>hbase.hregion.impl</name>
     <value>org.apache.hadoop.hbase.regionserver.IdxRegion</value>
   </property>
   

   
   
2. Make sure that ihbase-*.jar and commons-lang version 2.4 jar are added to the hbase classpath (you’ll need to edit hbase-env.sh)
3. When creating a table define which columns to index using IdxColumnDescriptor. The supported types are all the java primitive data types as well as byte[], char[] and BigDecimal
   

   Example: Creating an HTable with an index on family:qual column
   Note that this snippet below assumes that all the values assigned to family:qual are exactly 8 bytes, preferably created using Bytes.toBytes(long). The table may have rows in which family:qual is missing, those rows will not be included in the index.

   
   

   byte[] tableName = Bytes.toBytes(“table”);
   byte[] familyName = Bytes.toBytes(“family”);
   byte[] qualifier = Bytes.toBytes(“qual”);
   IdxColumnDescriptor idxColumnDescriptor = new IdxColumnDescriptor(familyName);
   IdxIndexDescriptor indexDescriptor = new IdxIndexDescriptor(qualifier, IdxQualifierType.LONG);
   idxColumnDescriptor.addIndexDescriptor(indexDescriptor);
   HTableDescriptor htd = new HTableDescriptor(tableName);
   htd.addFamily(idxColumnDescriptor);
   HBaseConfiguration conf = new HBaseConfiguration();
   HBaseAdmin admin = new HBaseAdmin(conf);
   admin.createTable(htd);
   HTable table = new HTable(conf, htd.getName());
   . . .
   

4. When scanning make sure you instantiate an instance of IdxScan and that you set the Expression property

Indexed scans notes

• When creating an IdxScan instance you must provide both an expression and filter. The filter is essential for correct scan results
• The index expression must accept any row accepted by the filter
• The filter may accept a subset of the rows accepted by the index expression (e.g. narrow down the results set)
• Setting a filter without setting an expression is supported and would revert to a ‘good old scan’
• The supported expression types are comparison, and, or. Comparisons support GT, GTE, EQ, LTE, LT
• The caller may combine any number of index expressions using any of the existing indexes. Trying to add an expression for a non-indexed column would result in a runtime error
  

  byte[] tableName = Bytes.toBytes(“table”);
  . . .
  IdxScan idxScan = new IdxScan();
  idxScan.setExpression(Expression.comparison(familyName, qualifier, Comparison.Operator.EQ, Bytes.toBytes(42L));
  idxScan.setFilter(new SingleColumnValueFilter(familyName, qualifier, CompareFilter.CompareOp.EQUAL, Bytes.toBytes(42L)));
  idxScan.setCaching(1000);
  ResultScanner scanner = table.getScanner(idxScan);
  for (Result res : scanner) {
  // Do stuff with res
  }