Rather than making an individual SET query for each and every parameter specified for a callproc call, use one single call instead, saving round-trip time (if one has more than one parameter). This can be significant if one is making many repeated callproc calls which have multiple arguments.

Then only downside I can think of is that if one or more arguments are quite large, combining them all could hit the max_allowed_packet limit. However, if it is only e.g. one large argument this will make next to no difference and the user should have an increased max_allowed_packet value in anticipation of e.g. larger blobs already.

Edit: As far as I can tell the CI test failures are nothing to do with my change, producing errors about invalid syntax for unrelated queries. test_callproc in fact passes.