I believe we are not currently storing references in text. Let's make sure we do that soon enough. <- outdated, might go with another approach
We plan to solve this by setting up a new External Store (one that will only be used by Flow) then migrating Flow to use that (details at T107610: Setup separate logical External Store for Flow in production). That will then free up the non-Flow one to use the normal compression procedure.
foreachwikiindblist flow.dblist extensions/Flow/maintenance/FlowExternalStoreMoveCluster.php