Commit 911e7020770 added a variety of new support routines to index
AMs. For example, it added a support function 5 to btree (see
BTOPTIONS_PROC), but didn't document this alongside the other support
functions in btree.sgml.
It looks like the new support functions are fundamentally different to
the existing ones in that they exist only as a way of supplying
parameters to other support functions. The idea was to preserve
compatibility with the old support function signatures. Even still, I
think that the new support functions should get some mention alongside
the older support functions.
I also wonder whether or not xindex.sgml needs to be updated to
account for opclass parameters.
--
Peter Geoghegan