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
qr.close( );
		myDataEngine.shutdown( );
		assertTrue( getDataSetCacheManager( myDataEngine ).doesLoadFromCache( ) );
		assertFalse( getDataSetCacheManager( myDataEngine ).doesSaveToCache( ) );
		getDataSetCacheManager( myDataEngine ).resetForTest( );
	}
	/**
	 * Return query result
	 * @param expectedLen
	 * @param qd
	 * @param gdArray
	 * @param beArray
	 * @param columStr
	 * @return query string output
	 * @throws Exception
	 */
	private String getOutputStrForGroupTest( int expectedLen,
			QueryDefinition qd, int groupDefCount, String[] beArray,
			String[] columStr ) throws Exception
	{
		StringBuffer sBuffer = new StringBuffer( );
		
		IResultIterator ri = newDataEngine( ).prepare( qd, appContextMap )
				.execute( null )
				.getResultIterator( );
		String metaData = "";
		for ( int i = 0; i < columStr.length; i++ )
		{
			metaData += formatStr( columStr[i], expectedLen );
		}