input for export to excel

Hi!

From where the export to excel process takes the information to fill the excel file?

Does it takes from memory? from the jasperprint object?

or does it runs again the report's query?

I'm asking this beacuse I'm looking to understand how does it works regarding to improve the time that takes a report to runs and export to excel.

For example, one report returns the results in 60 seconds and the export process  taks another 60 seconds to prepare the excel file.

Hope some one can help me

Thanks in advance.