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
{
				cacheDirStr = (String) cacheMap.get( dsAndDs );
				if ( cacheDirStr != null
						&& new File( cacheDirStr ).exists( ) == true )
				{
					return false;
				}
				else
				{
					cacheMap.put( dsAndDs, folderUtil.createSessionTempDir( ) );
					return true;
				}
			}
		}
	}
	/**
	 * @param dsAndDs
	 * @return
	 */
	boolean doesLoadFromCache( DataSourceAndDataSet dsAndDs )
	{
		String cacheDirStr = null;
		synchronized ( cacheMap )
		{
			cacheDirStr = (String) cacheMap.get( dsAndDs );
		}
		if ( cacheDirStr != null && new File( cacheDirStr ).exists( ) == true )
			return true;
		else
			return false;