Full-text search engine for associations w/ values

I am looking for a full-text search engine compatible with Rails that can
handle associations with a value in the join table with equality and
inequalities. For example, database of items with searchable titles and
descriptions and tags possibly with values:

"Hello" AND tag:release <= 0.4 AND tag:due < '2009-01-01' AND tag:important

An item with "Hello" in one of the indexed fields, "release", "due", and
"important" tags. The value of the "release" tag is less than or equal to
"0.4" (string or floating point compare okay), "due" date is this year or