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
if ( sql != null )
				break;
		}
		if ( sql == null )
			return null;
		if ( !( dataSetDesign instanceof OdaDataSetDesign ) )
			return null;
		sql = this.resetQueryText( sql );
		if ( sql == null || "".equals( sql ) )
		{
			return null;
		}
		QueryDefinition qd = new QueryDefinition( );
		qd.setDataSetName( dataSetDesign.getName( ) );
		String queryBack = ( (OdaDataSetDesign) dataSetDesign ).getQueryText( );
		( (OdaDataSetDesign) dataSetDesign ).setQueryText( sql );
		qd.setAutoBinding( true );
		IResultIterator iterator = this.dataEngine.prepare( qd )
				.execute( null )
				.getResultIterator( );
		( (OdaDataSetDesign) dataSetDesign ).setQueryText( queryBack );
		return iterator;
	}
	private String getQualifiedSql( ArrayList list, int index, String sql )
	{
		{
			ArrayList item = (ArrayList) list.get( index );
			if ( item == null || item.size( ) == 0 )
			{
				sql = null;