Greg Stark suggests here: http://archives.postgresql.org/pgsql-hackers/2005-05/msg00966.php that GiST could also be fixed to work with any subset of the index columns, but it hasn't been done yet, unless Teodor and Oleg snuck something in during that last round of GiST work.
GiST may work with any subset of index columns too. Even in existing code I don't see any problem except NULL in a first column. GiST doesn't store tuples with leading NULL value (gist.c lines 174, 326), so index doesn't contained them.
After our work about WAL-lization GiST, it may work with "invalid" tuples (possibly occured after crash recovery), so itsn't a big deal to add support NULL in a first column. But freeze date is outdated... Should I add or leave it to 8.2?
-- Teodor Sigaev E-mail: teodor@xxxxxxxxx WWW: http://www.sigaev.ru/ ---------------------------(end of broadcast)--------------------------- TIP 2: Don't 'kill -9' the postmaster