Bug 211839 String grouping unit type needs to support interval range.
Build ID: I20071101-2000 As Chart has supported, the String grouping unit type can be set interval range, the interval range means that the string group will base on row count distinction. For instance, let's say we have a,b,c,d,e,f,g , and set interval range to 2, the grouping result should be a,c,e,g. Now it is a requirement that DtE support the grouping type.
data/org.eclipse.birt.data.tests/test/org/eclipse/birt/data/engine/binding/DataSetCacheTest.java
assertTrue( getDataSetCacheManager( myDataEngine ).doesLoadFromCache( ) );
		assertFalse( getDataSetCacheManager( myDataEngine ).doesSaveToCache( ) );
		getDataSetCacheManager( myDataEngine ).resetForTest( );
		myDataEngine.shutdown( );
	}
	/**
	 * Test feature of cancel cache. This test case may fail in some cases. 
	 * @throws BirtException
	 */
	/**
	 * Test feature of whether cache will be used
	 * @throws BirtException
	 */
	public void testUseCache1( ) throws BirtException, Exception
	{
		this.dataSet.setCacheRowCount( 100 );
		myDataEngine = newDataEngine( );
		assertFalse( getDataSetCacheManager( myDataEngine ).doesLoadFromCache( ) );
		assertFalse( getDataSetCacheManager( myDataEngine ).doesSaveToCache( ) );
		executeQuery(myDataEngine);
	}
	private void executeQuery(DataEngineImpl myDataEngine) throws BirtException, DataException, Exception, IOException {
		QueryDefinition qd = this.newReportQuery( );
		rowBeArray = getRowExpr( );
		totalBeArray = getAggrExpr( );
		bindingNameRow = getRowExprName( );
		bindingExprRow = getAggrExprName( );
		prepareExprNameAndQuery( rowBeArray,
				bindingNameRow,
				totalBeArray,