It’s not my dashboard, but asking for a coworker. She has a rather complicated BAQ, which runs relatively fast if you run it with no filters. The Dashboard has 4 filters, and specifying a value in any of the fields causes the query to run MUCH slower, 5-6 times as long to return results. How would she go about troubleshooting this? Is there something obvious to look for?
Is it a single dashboard (just one BAQ, and no sub panels)?
I’ve read on here that Dashboard filters are supposed to actually change the dataset returned by the BAQ. Instead of just pulling the full (no filters dataset), and then applying the filters. So a field that you (ah-hem “your coworker” 
) are filtering on, may actually make the resulting query that is run, very complicated.
If a field the filter is for, actually comes from a calculation in a sub query, that might cause it to run the sub query first, then applying that filter to that subset of data, before using it with the top level query.
That sounds right to me. I’ll pass the information on. I just hadn’t run into this before since that’s a part of the system I don’t work on.
I end up with dashboards that run slowly no matter what, never ones that gets slower with filters 
If that turns out to be the case, I wonder if making a calculated field that is just a copy of the filed from a subquery, would help
Like if your BAQ returned a column SubQ3_MaxInvoiceNum (which is a calculated field in subqry3), and you were filtering on that. If you made a calc field (in the top level subqry),
Calc_MaxInvNum = SubQ3_MaxInvoiceNum;
Then put the dashboard filter on Calc_MaxInvNum, instead of SubQ3_MaxInvoiceNum