GiST subsplit question

http://archives.postgresql.org/message-id/CAEsn3ybKcnFno_tGQDJ=AfHiR2xd9KA1FQt5CQxxYu3Wz_hAHQ@mail.gmail.com

I was trying to answer that question on -general, and I found it a
little more challenging than I expected.

There was a previous discussion here:
http://archives.postgresql.org/pgsql-general/2007-08/msg01816.php

And it seems to trace back to these commits:
http://git.postgresql.org/gitweb/?p=postgresql.git;a=commit;h=783a73168b972488f85e48381546db047cb8f982
http://git.postgresql.org/gitweb/?p=postgresql.git;a=commit;h=1f7ef548ec2e594fa8766781c490fb5b998ea46b

I looked for the follow-up commit to support subsplit in the contrib
modules, figuring that would answer some questions, but I couldn't find
it.

The part that's confusing me is that the commit message says: "pickSplit
should set spl_(l|r)datum_exists to 'false'", but I don't see any
picksplit method that actually does that in contrib, nor in the sample
in the docs.

The code in that area is a bit difficult to follow, so it's not obvious
to me exactly what is supposed to happen.

So, do we demote that message to a DEBUG1? Or do we make it more clear
what the authors of a specific picksplit are supposed to do to avoid
that problem? Or am I misunderstanding something?

Regards,
Jeff Davis