Bug 180189 Support in memory data set cache.
Currently, Design-Time Data Cache is stored on disks. By performance tests using ramdisk, we found that caching in physical memory can improve the performance of RunAndRender by 30%.
data/org.eclipse.birt.data.tests/test/org/eclipse/birt/data/engine/binding/DataSetCacheTest.java
new ScriptExpression( "dataSetRow.CITY" ) );
		subqueryDefn.setApplyOnGroupFlag( false );
		qd.addSubquery( subqueryDefn );
		
		IQueryResults qr = myDataEngine.prepare( qd, appContextMap )
				.execute( null );
		assertTrue( qr.getResultMetaData( ) != null );
		return qr.getResultIterator( );
	}
	/**
	 * @throws BirtException 
	 * 
	 */
	public void testScriptedCache( ) throws BirtException
	{
		genCache2( );
		useCache2( );
	}
	/**
	 * @throws BirtException
	 */
	private void genCache2( ) throws BirtException
	{
		DataEngineContext context = DataEngineContext.newInstance( DataEngineContext.DIRECT_PRESENTATION,
				null,
				null,
				null );
		context.setCacheOption( DataEngineContext.CACHE_USE_ALWAYS, 4 );
		DataEngine myDataEngine2 = DataEngine.newDataEngine( context );
		IResultIterator ri = getResultIterator2( myDataEngine2 );