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/src/org/eclipse/birt/data/engine/executor/CacheMapManager.java
private String getMetaDataLoadFolder( DataSourceAndDataSet dsAndDs )
	{
		Object key = getKey( dsAndDs );
		if ( key != null )
			return String.valueOf( cacheMap.get( key ) );
		return null;
	}
	/**
	 * Return a matched key DataSourceAndDataSet instance. Please note that we
	 * do not include parameter during the comparation.
	 * 
	 * @param dsAndDs
	 * @return
	 */
	private Object getKey( DataSourceAndDataSet dsAndDs )
	{
		for ( Iterator it = cacheMap.keySet( ).iterator( ); it.hasNext( ); )
		{
			DataSourceAndDataSet temp = (DataSourceAndDataSet) it.next( );
			if ( temp.isDataSourceDataSetEqual( dsAndDs, false ) )
			{
				return temp;
			}
		}
		return null;
	}
	/**
	 * Folder util class to manager temp folder
	 */
	private class FolderUtil