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
* @throws BirtException
	 */
	public void testSubqueryCache( ) throws BirtException
	{
		genCache3( );
		useCache3( );
	}
	/**
	 * @throws BirtException
	 */
	private void genCache( ) throws BirtException
	{
		this.dataSet.setCacheRowCount( 4 );
		DataEngine myDataEngine = newDataEngine( );
		IResultIterator ri = getResultIterator1( myDataEngine );
		while ( ri.next( ) )
		{
			for ( int i = 0; i < bindingNameRow.length; i++ )
				expectedValue.add( ri.getValue( bindingNameRow[i] ) );
			for ( int i = 0; i < totalBeArray.length; i++ )
				expectedValue.add( ri.getValue( bindingExprRow[i] ) );
		}
		ri.close( );
		myDataEngine.shutdown( );
	}
	/**
	 * @throws BirtException
	 */
	private void genCache3( ) throws BirtException
	{