The bigger problem, would be the full text search engine. Just regexing or indexing through documents in real time does not scale well.

Look at DBIx::TextIndex. I have been using for a little while now and it works well. It also gives you grouping, boolean ops ('AND', 'OR', & 'NOT'), phrase search, and wildcards.

I had problems using DBIx::TextIndex with PostgreSQL v8 but it should work with PostgreSQL v7. It also works with MySQL or SQLite.