[0.13.x] help with poor personal roboport performance

[jojo_steed]

Since updating to 0.13.x I've noticed a marked drop in performance for my personal roboports, often taking up to 10 seconds to realise that there are unbuilt ghosts right next to my character. What i've been able to find on the subject suggests this is likely to be a symptom of having a large number (>600) of pending build jobs. I guess this is a lot more likely now that ghosts placed by the player do not expire and i might well have accumulated a whole bunch of stuff around the edges of construction coverage without realising.

My question is this: Is there a command that can show me the number of pending construction jobs, their locations, and possibly clear them? I've got a pretty big factory and I've done a lot of running around but haven't spotted anything that looks like it could be the cause.