Unfortunately I don't have access to this transaction. We have asked again and again our IT department to make more fields available in the reports, but they're either unskilled to do that or busy, or both. I'm lucky the SQ01 & SQ02 transactions have been left open by our integrators, so this seems to be my only available option at the moment.
However, querying SDF seems fast enough if some of the selection parameters provided by the logical database are set (such as document n°). It it slow if the only criteria defined are those that I've added to the selection screen in the query's configuration (SQ01 > Modify), such as vendor id...
I'm guessing the system is processing too much data, then applying the selection parameters over it later. If that is the case, is there a way to make that selection earlier?