The performance improvements are nice, but breaking a published API is less nice particularly since some work has been done to make pglz more plugabble (see 60838df9, guess how wrote that).
I don't think that should stop us from breaking the API. You've got to do quite low level stuff to need pglz directly, in which case such an API change should be the least of your problems between major versions.
I was going to say that the function is only used twice in the code base, but I see it’s now used four times. So maybe leave the old signature in place and add the new one for my purposes after all. Though with only four internal calls, I am guessing Michael is more concerned about external users than with internal ones?
