SQL Server 2008 Full Text Search (FTS) versus Lucene.NET

Question

I know there have been questions in the past about SQL 2005 versus Lucene.NET but since 2008 came out and they made a lot of changes to it and was wondering if anyone can gi

Answer 1

I built a medium-size knowledge base (maybe 2GB of indexed text) on top of SQL Server 2005's FTS in 2006, and have now moved it to 2008's iFTS. Both situations have worked well for me, but the move from 2005 to 2008 was actually an improvement for me.

My situation was NOT like StackOverflow's in the sense that I was indexing data that was only refreshed nightly, however I was trying to join search results from multiple CONTAINSTABLE statements back in to each other and to relational tables.

In 2005's FTS, this meant each CONTAINSTABLE would have to execute its search on the index, return the full results and then have the DB engine join those results to the relational tables (this was all transparent to me, but it was happening and was expensive to the queries). 2008's iFTS improved this situation because the database integration allows the multiple CONTAINSTABLE results to become part of the query plan which made a lot of searches more efficient.

I think that both 2005 and 2008's FTS engines, as well as Lucene.NET, have architectural tradeoffs that are going to align better or worse to a lot of project circumstances - I just got lucky that the upgrade worked in my favor. I can completely see why 2008's iFTS wouldn't work in the same configuration as 2005's for the highly OLTP nature of a use case like StackOverflow.com. However, I would not discount the possibility that the 2008 iFTS could be isolated from the heavy insert transaction load... but it also sounds like it could be as much work to accomplish that as move to Lucene.NET ... and the cool factor of Lucene.NET is hard to ignore ;)

Anyway, for me, the ease and efficiency of SQL 2008's iFTS in the majority of situations probably edges out Lucene's 'cool' factor (though it is easy to use, I've never used it in a production system so I'm reserving comment on that). I would be interesting in knowing how much more efficient Lucene is (has turned out to be? is it implemented now?) in StackOverflow or similar situations.