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/DataSetCacheManager.java
populateDataSetRowMapping( metaMap );
				( (ResultClass) rsClass ).doSave( bos1, metaMap );
				bos1.close( );
				fos1.close( );
				FileInputStream fis = new FileInputStream( metaFile );
				BufferedInputStream bis = new BufferedInputStream( fis );
				rowCount = IOUtil.readInt( bis );
			}
			catch ( IOException e )
			{
				throw new DataException( ResourceConstants.DATASETCACHE_SAVE_ERROR,
						e );
			}
		}
		/**
		 * Populate the new rsClass object instance
		 * 
		 * @param metaMap
		 * @throws DataException
		 */
		private void populateDataSetRowMapping( Map metaMap )
				throws DataException
		{
			for ( int i = 0; i < rsClass.getFieldCount( ); i++ )
				metaMap.put( rsClass.getFieldName( i + 1 ),
						new ScriptExpression( ExpressionUtil.createJSDataSetRowExpression( rsClass.getFieldName( i + 1 ) ) ) );
		}
	}
}