<p>What is the best way to create reverse index for full text search in Common Lisp ? Is there any proven and (relatively) bug-free open library for SBCL or LispWorks ?</p>

<p>I managed to create my own library on top of AllegroCache - it was fairly easy to create, reliable and fast, but lacks advanced search options (phrases, wildcarded words in phrases, etc).</p>

<p>Is there any open library that can be used with SBCL or LispWorks so I don't have to reinvent the wheel by writing my own ?</p>

I know you're asking about Common Lisp, but there are a number of inverted text search service oriented applications.   One well known and respected on is
Lucene
.
Could a solution be to use that search engine, but interface your Common Lisp code via a web-service API?  (xml-rpc, xml over http or just text over http)?
Is there a further reason why you'd like it to be in Common Lisp?  Packages like Lucene may cover all the search related features you need, while using a remote api may still allow you to perform your more complex logic in Common Lisp.