This is at least cross-platform, but it's also sort of what the postgres fulltext feature does. The postgres fulltext should still run faster though, and I think it uses much more compact storage than creating one row per keyword per original object with a b-tree on the whole thing.

Also debatable which is "simpler", because with a table of keyword-to-record-id you have to maintain that yourself. With the one I showed, once you get the table and query set up, postgres does all the work to maintain the index.