Issue: The XLS gradebook export is timing out when generating an export for courses that have thousands of student enrollments, and numerous grade items. 

When we took a look at what is going on through our monitoring tools, the database query for the information takes seconds to resolve but the /grade/export/xls/index.php process has to build each and every cell of the XLS spreadsheet to be exported, and this is where its timing out. 

By contrast running the "Plain Text Format" (CSV) export (/grade/export/txt/index.php) takes only a few seconds, and the output file looks identical to what is shown when opening a XLS file. This is currently the workaround we have the client using.

Possible suggestions as to what can be done:
1) Remove the XLS option and rename "Plain Text Format" to CSV/XLS export

2) Make it such that when the XLS export is called its just running a CSV export