Our Impression/Click report is using pipe delimiter to instead of commas delimiter, which will be helpful to load the report more than 300k rows.
Here's the way to show you how to use pipe delimiter, you can also check the link here from Microsoft:
Select the cell or column that contains the text you want to split.
Select Data > Text to Columns.
In the Convert Text to Columns Wizard, select Delimited > Next.
Select the Delimiters for your data. For example, Comma and Space or '|'. You can see a preview of your data in the Data preview window.
Select the Column data format or use what Excel chose for you.
Select the Destination, which is where you want the split data to appear on your worksheet.
Feel free to let us know if you have any questions via email@example.com or chat with us.