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/impl/PreparedJointDataSourceQuery.java
}
			leftPrefix = leftPrefix + COLUMN_NAME_SPLITTER;
			rightPrefix = rightPrefix + COLUMN_NAME_SPLITTER;
			JointResultMetadata meta = populatorJointResultMetadata( left,
					leftPrefix,
					right,
					rightPrefix );
			return meta;
		}
		catch ( BirtException be )
		{
			throw DataException.wrap( be );
		}
	}
	/**
	 * Get the data set name with out library name prefix. This fix
	 * is for bugzilla bug 155848. 
	 * 
	 * @param qualifiedName
	 * @return
	 */
	private String getDataSetName( String qualifiedName )
	{
		return ExpressionUtil.getDataSetNameWithoutPrefix( qualifiedName );
	}
	
	/**
	 * Gets the Java class used to represent the specified data type.
	 * 
	 * @param typeCode