Slow performance when exporting for non admin users

Problem/Motivation

When exporting a view to CSV using this module, it is taking significantly longer to produce the file for non-admin users than other users. For a particular view it took 4 seconds to produce the download link for an admin and 1.5 minutes for a non-admin. This was from the same machine at the same time using the same internet access. This has also been tested at alternative locations using other user accounts.

Things I have tried:

• Checked and changed permissions.
• Changed the query options to disable sql rewriting.
• Changed between batched on and off.
• Changed size of batched.
• Set a limit to export.
• Changed the items to display to 1.

Unfortunately, none of these have made a difference and no errors are being logged.

Steps to reproduce

Create a view with a Page and a Data Export (csv). View the page and click CSV download button when logged in as an admin. Reproduce when logged in as an authenticated user.