FYI - the intarray contrib module for Postgres does support indexing of arrays of integers.

http://www.postgresql.org/docs/9.1/static/intarray.html#AEN1...

And it happens to use bloom filters under-the-hood to do it.

From the docs:

"Two GiST index operator classes are provided: gist__int_ops (used by default) is suitable for small- to medium-size data sets, while gist__intbig_ops uses a larger signature and is more suitable for indexing large data sets (i.e., columns containing a large number of distinct array values). The implementation uses an RD-tree data structure with built-in lossy compression."

That bit about the lossy compression in the implementation if referencing the use of a bloom filter. Also mentioned here, http://archives.postgresql.org/pgsql-hackers/2005-05/msg0147...