Posted 8 September 2017, 2:45 pm EST
I encountered a number of Excel files that were taking an extraordinarily long time to open. Via process of elimination I determined that it was due to conditional formatting being applied to an entire column.
By default Excel shows 68 thousand rows. If the user applied conditional formatting on an entire column, even though there may be only a couple of hundred rows containing actual data, the OpenExcel command appears to process all 68 thousand rows. If I remove the conditional formatting and make sure it is only applied to the rows containing data, the import action occurs as the expected speed.
Applying conditional formatting for an entire column is a fairly common action for Excel users. Spread should really ignore these 68 thousand empty row and import at the usual speed.
(Note that using the "DataOnly" flag also solves this issue, however this is an inadequate solution as one loses other important data such as formatted dates, etc.)